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 <chapter id="hardsums">
 <chapterinfo>
 <authorgroup>
 <author>
 <firstname>Pamela</firstname>
 <surname>Robert</surname>
 <affiliation>
 <address><email>pamroberts@blueyonder.co.uk</email></address>
 </affiliation>
 </author>
 <author>
 <firstname>Anne-Marie</firstname>
 <surname>Mahfouf</surname>
 <affiliation>
 <address><email>annemarie.mahfouf@free.fr</email></address>
 </affiliation>
 </author>
 <!-- TRANS:ROLES_OF_TRANSLATORS -->
 </authorgroup>
 </chapterinfo> 
 <title>Advanced &sheets;</title>
 <sect1 id="series">
 <title>Series</title>
 <para>When constructing a spreadsheet you often need to include a series of
 values, such as 10, 11, 12..., in a row or column. There are several ways you
 can do this in &sheets;.</para>
 <para>For a simple short series such as 5, 6, 7, 8... the <quote>Drag and Copy
 </quote> method is the simplest. Enter the starting value into the starting
 cell and the next value of the series into an adjacent cell.
 Then select both cells and move the mouse pointer so that it is over the small
 square at the bottom right corner; the cursor will change to a
 diagonal double headed arrow. Then hold the <mousebutton>left</mousebutton>
 mouse button down while you drag the cells down or across as needed.</para>
 <para>The step size is calculated as the difference between the two starting
 values that you have entered.
 For example if you enter <userinput>4</userinput> into cell A1 and 
 <userinput>3.5</userinput> into A2 then select both cells and Drag and Copy 
 them down, the step size will be the value in A2 minus the value 
 in A1, -0.5 in this case so you will get the series 4, 3.5, 3, 2.5, 2...</para>
 
 <para>The <quote>Drag and Copy</quote> method will even cope with series where 
 the step value is not a constant value but is itself a series. So that if you 
 start with 1, 3, 4, 6 Drag and Copy will extend it to 1, 3, 4, 6, 7, 9, 10, 
 12..., the step value in this example being the series 2, 1, 2, 1...</para>
 
  <!--FIXME does not work here -->
 <para>&sheets; also recognizes some special <quote>series</quote> such as
 the days of the week. Try entering <userinput>Friday</userinput> into a cell 
 (note the capitalization) then Drag and Copy it down. To see what special series 
 are available, and perhaps create your own, select <menuchoice><guimenu>Tools</guimenu>
 <guimenuitem>Custom Lists...</guimenuitem></menuchoice></para>
 
 <para>If you select a cell and choose <guimenuitem>Series...</guimenuitem> 
 from the <guimenu>Insert</guimenu> menu you will see the <guilabel>Series</guilabel> 
 dialog box. This is useful for creating series that are too long 
 to be conveniently constructed using the Drag and Copy method, or for 
 creating geometric series such as 1, 1.5, 2.25, 3.375... where the step value,
 1.5 in this case, is used as a multiplier.</para>
 <para>If the type of series that you want is too complicated for any of the 
 previous methods, consider using a formula and Drag and Copying that. For 
 example to create a series with the values 2, 4, 16, 256... enter 
 <userinput>2</userinput> into A1, <userinput>=A1*A1</userinput> into A2, and 
 Drag and Copy cell A2 down.</para>
 </sect1>
 
 <sect1 id="formulas">
 <title>Formulae</title>
 <sect2 id="builtin">
 <title>Built in Functions</title>
 <para>&sheets; has a huge range of built in mathematical and other 
 <link linkend="functions">functions</link> 
 that can be used in a formula cell. They can be seen and accessed by selecting 
 a cell then choosing <guimenuitem>Function...</guimenuitem> from the 
 <guimenu>Insert</guimenu> menu. This brings up the <guilabel>Function</guilabel> 
 dialog box.</para>
 <para>Select the function you want to use from the listbox at the left of the 
 dialog box. The <guilabel>Help</guilabel> tab page will then display a description,
 the return type, Syntax, Parameters, and Examples for this function.
 In addition this page provides often links to Related Functions. 
 Then press the button with the down arrow key symbol on it to paste 
 it into the text edit box at the bottom of the dialog.</para>
 <para>The <guilabel>Parameters</guilabel> tab page will then be displayed 
 to let you enter the parameter(s) for the function you have just 
 chosen. If you want to enter an actual value for a parameter, just type it 
 into the appropriate text box in the <guilabel>Parameters</guilabel> page. To
 enter a cell reference rather than a value, <mousebutton>left</mousebutton> 
 click on the appropriate text box in the <guilabel>Parameters</guilabel> page;
 then <mousebutton>left</mousebutton> click on the target cell in 
 the spreadsheet.</para>
 <para>Instead of using the <guilabel>Parameters</guilabel> page, cell 
 references such as <userinput>B6</userinput> can be entered by typing them 
 directly into the edit box at the bottom of the <guilabel>Function</guilabel> 
 dialog. If a function has more than one parameter separate them with a 
 semi-colon (<keysym>;</keysym>).</para>
 <para>Pressing the <guibutton>OK</guibutton> button will insert the 
 function into the current cell and close the <guilabel>Function</guilabel>
 dialog.</para>
 <para>You can of course do without the <guilabel>Function</guilabel> 
 dialog and simply type the complete expression into the main text entry box 
 in the <guilabel>Cell Editor</guilabel> tool options. 
 Function names are not case sensitive. Do not forget that all 
 expressions must start with an <keysym>=</keysym> symbol.</para>
 </sect2>
 
 <sect2 id="logical">
 <title>Logical Comparisons</title>
 <para>Logical functions such as IF(), AND(), OR() take parameters which have the 
 logical (boolean) values True or False. This type of value can be produced by 
 other logical functions such as ISEVEN() or by the comparison of values in 
 spreadsheet cells using the comparison expressions given in the following 
 table.</para>
 
 <informaltable><tgroup cols="3">
 <thead>
 <row>
 <entry> Expression </entry>
 <entry> Description </entry>
 <entry> Example </entry></row>
 </thead>
 <tbody>
 
 <row><entry><keysym>=</keysym><keysym>=</keysym></entry>
 <entry>Is equal to</entry>
 <entry><userinput>A2==B3</userinput> is True if the value in A2 is equal to 
 the value in B3</entry>
 </row>
 
 <row><entry><keysym>!</keysym><keysym>=</keysym></entry>
 <entry>Is not equal to</entry>
 <entry><userinput>A2!=B3</userinput> is True if the value in A2 is not equal 
 to the value in B3</entry>
 </row>
 
 <row><entry><keysym>&lt;</keysym><keysym>&gt;</keysym></entry>
 <entry>Is not equal to</entry>
 <entry>Same as <userinput>A2!=B3</userinput></entry>
 </row>
 
 <row><entry><keysym>&lt;</keysym></entry>
 <entry>Is less than</entry>
 <entry><userinput>A2&lt;B3</userinput> is True if the value in A2 is less than 
 the value in B3</entry>
 </row>
 
 <row><entry><keysym>&lt;</keysym><keysym>=</keysym></entry>
 <entry>Is less than or equal to</entry>
 <entry><userinput>A2&lt;=B3</userinput> is True if the value in A2 is less than 
 or equal to the value in B3</entry>
 </row>
 
 <row><entry><keysym>&gt;</keysym></entry>
 <entry>Is greater than</entry>
 <entry><userinput>A2&gt;B3</userinput> is True if the value in A2 is greater 
 than the value in B3</entry>
 </row>
 
 <row><entry><keysym>&gt;</keysym><keysym>=</keysym></entry>
 <entry>Is greater than or equal to</entry>
 <entry><userinput>A2&gt;=B3</userinput> is True if the value A2 is greater than 
 or equal to the value in B3</entry>
 </row>
 
 </tbody></tgroup></informaltable>
 
 <para>Thus if you enter <userinput>=IF(B3&gt;B1;"BIGGER";"")</userinput> into 
 a cell it will display BIGGER if the value in B3 is greater than that in B1, 
 otherwise the cell will show nothing.</para>
 </sect2>
 
 <sect2 id="absolute">
 <title>Absolute Cell References</title>
 <para>If a formula contains a cell reference that reference will normally be 
 changed when the cell is copied to another part of the worksheet. To prevent 
 this behavior put a <keysym>$</keysym> symbol before the column letter, row 
 number or both. </para>
 
 <itemizedlist>
 <listitem><para>
 If A1 contains the formula <userinput>=D5</userinput> then on copying the 
 cell to B2 it will become <userinput>=E6</userinput> (the normal behavior).
 </para></listitem>
 <listitem><para>
 If A1 contains the formula <userinput>=$D5</userinput> then on copying the 
 cell to B2 it will become <userinput>=D6</userinput> (column letter not 
 changed).
 </para></listitem>
 <listitem><para>
 If A1 contains the formula <userinput>=D$5</userinput> then on copying the 
 cell to B2 it will become <userinput>=E5</userinput> (row number not 
 changed).
 </para></listitem>
 <listitem><para>
 If A1 contains the formula <userinput>=$D$5</userinput> then on copying the 
 cell to B2 it will remain as <userinput>=D5</userinput> (neither the column 
 letter nor the row number are changed). 
 </para></listitem>
 
 </itemizedlist>
 <para>When you are entering or editing a cell reference in a formula the 
 shortcut key <keysym>F4</keysym> can be used to step through these four 
 possibilities.</para>
 <para><link linkend="namedareas">Named cells</link> can be used in a similar 
 way to include a unchanging cell reference in a formula.
 </para>
 </sect2>
 </sect1>
 
 <sect1 id="sumspecialpaste">
 <title>Arithmetic using Special Paste</title>
 <para>Sometimes you may want to add a single value to a number of 
 cells, or subtract a value from them, or multiply or divide them all by a 
 single value. The <guimenuitem>Special Paste...</guimenuitem> option lets you 
 do this quickly and easily.</para>
 <para>First, enter the modifier value into any spare cell on your spreadsheet 
 and <guimenuitem>Copy</guimenuitem> it. Then select the area of cells you want 
 to change, choose <guimenuitem>Special Paste...</guimenuitem> from the 
 <guimenu>Edit</guimenu> or the context menu 
 and select <guilabel>Addition</guilabel>, <guilabel>Subtraction</guilabel>, 
 <guilabel>Multiplication</guilabel> or <guilabel>Division</guilabel> from the 
 <guilabel>Operation</guilabel> section of the dialog box.</para>
 <para>You can also apply different modifier values to different rows or 
 columns of the target area by copying an area containing the wanted modifiers 
 before selecting the target area and doing <guimenuitem>Special Paste...</guimenuitem>
 For example, if you enter <userinput>5</userinput> into cell 
 A1, <userinput>10</userinput> into B1, select both cells and do a <guimenuitem>
 Copy</guimenuitem> then <guimenuitem>Special Paste...</guimenuitem> <guilabel>
 Addition</guilabel> into cells A10 to D15, 5 will be added to A10:A15 and 
 C10:C15, and 10 to B10:B15 and D10:D15.</para>
 <para>Note that a modifier value can be a formula as well as a simple numeric 
 value. If it is a formula then &sheets; will adjust the cell references as 
 for a normal <guimenuitem>Paste</guimenuitem> operation.</para>
 </sect1>
 
 <sect1 id="arrayformulas">
 <title>Array Formulas</title>
 <para>&sheets; allows you to use formulas whose result is a matrix or a range
 of values. Normally, only the first value is displayed in a cell. If you would
 like to display the entire matrix, simply use <keycombo>&Ctrl;&Alt;&Enter;</keycombo> when editing
 a formula, and it will be converted into an array formula, occupying neighboring
 cells as needed.</para>
 <para>Cells that are a part of an array formula are locked for editing.</para>
 </sect1>
 
 <sect1 id="goalseek">
 <title>Goal Seeking</title>
 <para>&sheets; can be used to solve algebraic expressions such as <emphasis>
 x + x^2 = 4</emphasis> or <emphasis>For what value of x does x + x squared 
 equal 4 ?</emphasis></para>
 <para>For this example you could enter <userinput>=A2+A2*A2</userinput>
 into A1 then either try different values in A2 until the result in A1 is as 
 close as you wish to <emphasis>4</emphasis> or, preferably, use &sheets;'s  
 <guimenuitem>Goal Seek...</guimenuitem> feature which automatically adjusts the 
 value in one cell to try to make the value in another cell as close as 
 possible to a target value.</para>
 <para>It is invoked by selecting <guimenuitem>Goal Seek...</guimenuitem> from 
 the <guimenu>Data</guimenu> menu. This brings up a dialog box in which you 
 should enter the reference of the target value cell (<userinput>A1</userinput> 
 in this case) into the <guilabel>Set cell:</guilabel> box, the target value 
 itself (<userinput>4</userinput>) into the <guilabel>To value:</guilabel> box 
 and the reference of the cell that is to be changed 
 (<userinput>A2</userinput>) into the <guilabel>By changing cell:</guilabel> 
 box. Note that you need to have entered some initial value into the cell that 
 is to be changed before starting <guimenuitem>Goal Seek</guimenuitem>.</para>
 <para>Pressing the <guibutton>OK</guibutton> button will start the
 calculation. When it finishes and if it has found a solution press the
 <guibutton>OK</guibutton> button to accept the result or
 <guibutton>Cancel</guibutton> to keep the original value.
 </para>
 </sect1>
 
  <sect1 id="pivottable">
    <title>Pivot Tables</title>
    <para>
      &sheets; can be used to construct <ulink url="http://en.wikipedia.org/wiki/Pivot_table">pivot tables</ulink> using the data of the current table.
    </para>
    <para>This feature can be invoked by selecting <guimenuitem>Pivot...</guimenuitem> from 
      the <guimenu>Data</guimenu> menu. Below is an example of pivot table generation.
    </para>
    <para>
      Supposing we have the following data.
    </para>
    <para>
      <mediaobject>
        <imageobject>
          <imagedata fileref="pivot1.png" format="PNG"/>
        </imageobject>
        <textobject>
          <phrase>Initial table</phrase>
        </textobject>
      </mediaobject>
    </para>
    <para>
      We want to create a pivot table of our choice and requirement. So we choose
        <menuchoice>
          <guimenu>Data</guimenu>
          <guimenuitem>Pivot...</guimenuitem>
        </menuchoice>.
      </para>
      <para>
        The dialog box that will appear allows user to select the source of data. The data can be taken from the current worksheet or from an external source like a database or <abbrev>ODS</abbrev> file.
      </para>
      <para>
        <mediaobject>
          <imageobject>
            <imagedata fileref="pivot2.png" format="PNG"/>
          </imageobject>
          <textobject>
            <phrase>Choosing the data source</phrase>
          </textobject>
        </mediaobject>
      </para>
      <para>
        Here is the dialog box which allows the user to customize the pivot table. The column labels in the source data are converted to labels which serve as the working fields. The labels can be dragged and dropped into one of three areas (<guilabel>Rows</guilabel>, <guilabel>Columns</guilabel> or <guilabel>Values</guilabel>) to generate the pivot table. You can reset your choices using <guibutton>Reset DnD</guibutton> button.
      </para>
      <para>
        <mediaobject>
          <imageobject>
            <imagedata fileref="pivot3.png" format="PNG"/>
          </imageobject>
          <textobject>
            <phrase>Pivot table customization dialog</phrase>
          </textobject>
        </mediaobject>
      </para>
      <para>
        In our example, <replaceable>Name</replaceable> is dragged to <guilabel>Rows</guilabel>, <replaceable>Category</replaceable> to <guilabel>Columns</guilabel>, <replaceable>Score</replaceable> to <guilabel>Values</guilabel>. User defined functions like sum, average, max, min, count, &etc; can be selected from the <guilabel>Select Option</guilabel> list.
      </para>
      <para>
        The <guibutton>Add Filter</guibutton> button can be used to open filter dialog box to filter the desired data. Using this box you can define multiple filters based on the column label and the relationship between them (<guimenuitem>And</guimenuitem> or <guimenuitem>Or</guimenuitem>). This would allow extreme freedom to customize the output.
      </para>
      <para>
        <mediaobject>
          <imageobject>
            <imagedata fileref="pivot4.png" format="PNG"/>
          </imageobject>
          <textobject>
            <phrase>Pivot table filtering dialog</phrase>
          </textobject>
        </mediaobject>
      </para>
      <para>
        <guilabel>Total Rows</guilabel> and <guilabel>Total Columns</guilabel>: checking these allow automatic totalling of corresponding rows and columns in the pivot table.
      </para>
    </sect1>
 
 <sect1 id="worksheets">
 <title>Using more than one Worksheet</title>
 <para>When you start a new, empty, document with &sheets; it will create a 
 number of blank worksheets. The number of sheets it creates is determined 
 by the selected template.</para>
 <para><menuchoice><guimenu>Insert</guimenu><guimenuitem>Sheet</guimenuitem>
 </menuchoice> will add another sheet to the document.</para>
 <para>You can also switch between worksheets by using the 
 <keycombo action="simul">&Ctrl;<keysym>PgDown</keysym></keycombo> 
 to move to the next sheet, 
 <keycombo action="simul">&Ctrl;<keysym>PgUp</keysym></keycombo> to move to 
 the previous one.</para>
 <para>Worksheets are given the default names of <emphasis>Sheet1</emphasis>, 
 <emphasis>Sheet2</emphasis>... You can give a sheet a different name by 
 <mousebutton>right</mousebutton> clicking on the tab and selecting 
 <guimenuitem>Rename Sheet...</guimenuitem></para>
 <para>To remove a sheet from the document use the <guimenuitem>Remove Sheet
 </guimenuitem> option in the context menu 
 that pops up when you <mousebutton>right</mousebutton> click on the tab 
 for the sheet you want to remove.</para>
 <para>Other entries in the <menuchoice><guimenu>Format</guimenu><guisubmenu>
 Sheet</guisubmenu></menuchoice> submenu allow you to show or hide a sheet in 
 much the same way as rows and columns can be hidden.</para>
 <para>If you want a formula in one sheet to refer to a cell in another sheet, 
 the cell reference must start with the sheet name followed by an exclamation 
 mark (<keysym>!</keysym>). For example if you enter <userinput>=Sheet2!A2
 </userinput> into a cell in Sheet 1, that cell will take the value from A2 of 
 Sheet2. Note that sheet names are case sensitive.</para>
 
 
 <sect2 id="consolidate">
 <title>Consolidating Data</title>
 <para>You may have constructed a document containing several worksheets 
 containing similar data but for, say, different months of the year, and wish 
 to have summary sheet containing the consolidated (&eg;, sum or average) values 
 of the corresponding data items in the other sheets.</para>
 <para>This task can be made slightly easier by using the <guimenuitem>
 Consolidate...</guimenuitem> item from the <guimenu>Data</guimenu> menu.</para>
 <para>Selecting this option brings up the <guilabel>Consolidate</guilabel>
 dialog box.</para>
 <para>For each of the source sheets, enter a reference to the desired data area
 in the <guilabel>Reference:</guilabel> box. Press <guibutton>Add</guibutton> to
 transfer it to the <guilabel>Entered references:</guilabel> box. The reference
 should include the name of the sheet containing the source data, such as
 <userinput>January!A1:A10</userinput>, and can be entered automatically by
 selecting the area in the appropriate sheet.</para>
 <para>After entering the references for all of the source data sheets 
 select the cell in the target sheet where you want the top left corner of the 
 consolidated results to appear. Then choose the appropriate function from
 the <guilabel>Function:</guilabel> combo box and press the
 <guibutton>OK</guibutton> button.</para>
 <para>If you click the <guibutton>Details >></guibutton> in the dialog and check 
 the <guilabel>Copy data</guilabel> box the values resulting from the consolidation will 
 be placed into the target cells rather than the formulae to calculate them.
 </para>
 </sect2>
 </sect1>
 <sect1 id="insertchart">
 <title>Inserting a Chart</title>
 <para>You can insert a chart into a sheet to give a graphical view of your 
 data.</para>
 <para>First enable <guilabel>Add Shape</guilabel> docker using the <menuchoice>
 <guimenu>Settings</guimenu><guimenuitem>Dockers</guimenuitem>
 </menuchoice> menu item.</para>
 <para>Then select the area of cells containing the data and choose 
 <guilabel>Chart</guilabel> in the <guilabel>Add Shape</guilabel>. Drag the cursor across the sheet while holding the 
 <mousebutton>left</mousebutton> mouse button down to define the area where you want the 
 chart to appear, there is no need to be too accurate at this stage as the 
 chart size can easily be changed at any time. When you release the mouse 
 button a <guilabel>Chart Options</guilabel> dialog box will appear.</para>
 <para>The data area is already prefilled with the selected cell range.
 Select the first row and column as labels, check <guilabel>Data set in rows</guilabel>
 and click the <guibutton>OK</guibutton> button. The Dialog will vanish and you 
 will see the chart embedded into the worksheet.</para>
 <para>Now select <guibutton>Chart Editing Tool</guibutton> from the <guilabel>Tools</guilabel> 
 docker and edit the chart properties like chart type, labels and axis in the 
 <guilabel>Chart editing</guilabel>.</para>
 <para>
 <mediaobject>
 <imageobject>
 <imagedata fileref="chart1.png" format="PNG"/>
 </imageobject>
 <textobject>
 <phrase>Screenshot of embedded chart</phrase>
 </textobject>
 </mediaobject>
 </para>
 <para>To move, resize or even delete the embedded chart switch to the 
 <guibutton>Basic shape manipulation</guibutton> tool and click anywhere 
 within the chart area. It should now appear with a green border 
 and with a small yellow square at each corner and in the middle of each edge.
 </para>
 <para>If you move the cursor over any of the squares it should change 
 to a double headed arrow. You can resize the chart by dragging one of these 
 squares with the <mousebutton>left</mousebutton> mouse button pressed. To 
 delete the chart <mousebutton>right</mousebutton> click on one of the 
 squares and select <guimenuitem>Delete</guimenuitem>.</para>
 <para>To move the chart move the cursor into the chart. 
 The cursor should then change to a cross, press the 
 <mousebutton>left</mousebutton> mouse button and you will be able to drag the 
 chart to where you want it to be.</para>
 <para>To restore the chart to its normal appearance simply click anywhere 
 outside of the chart area.</para>
 <para>To change the format of the chart itself <mousebutton>left</mousebutton> 
 click twice within the chart area. The chart <guilabel>Chart editing</guilabel> 
 should appear in the docker. You can then 
 use these tools to change the chart.</para>
 </sect1>
 
 <sect1 id="insertdata">
 <title>Inserting External Data</title>
 <para>You can insert data from a text file or from the clipboard into a 
 worksheet by first selecting the cell where you want the top left item of the 
 inserted data to appear, then choosing <guimenuitem>From Text File...</guimenuitem> 
 or <guimenuitem>From Clipboard...</guimenuitem> from the 
 <menuchoice><guimenu>Insert</guimenu><guisubmenu>External Data</guisubmenu>
 </menuchoice> sub menu.</para>
 <para>In both cases &sheets; will assume that the data is in
 <acronym>CSV</acronym> form and will open a
 dialog box allowing you to control how the data is extracted from the file or
 clipboard and placed into the worksheet cells.</para>
 <para>If support for it has been included in your system, &sheets; can also
 insert data from a <acronym>SQL</acronym> database into a worksheet. This is
 done by using the <menuchoice><guimenu>Insert</guimenu><guisubmenu>
 External Data</guisubmenu><guimenuitem>From Database...</guimenuitem>
 </menuchoice> option.</para>
 </sect1>
 
 <sect1 id="hyper">
 <title>Link Cells</title>
 <para>A spreadsheet cell can be linked to an action so that <mousebutton>
 left </mousebutton> clicking on the cell will, for example, open your 
 browser. To make a cell act in this way select it and choose  
 <menuchoice><guimenu>Insert</guimenu><guimenuitem>Link...</guimenuitem>
 </menuchoice>. This will bring up the <guilabel>Insert Link</guilabel> 
 dialog box, which lets you choose between four types of link:</para>
 
 <itemizedlist>
 <listitem><para>An <guilabel>Internet</guilabel> link cell will try to 
 open your default browser at the &URL; entered in the 
 <guilabel>Internet address:</guilabel> text box of the <guilabel>Insert
 Link</guilabel> dialog when it is clicked. This could be, for example, 
 <userinput>http://www.calligra.org</userinput>. 
 </para></listitem>
 
 <listitem><para>Clicking on a cell containing a <guilabel>Mail</guilabel> 
 link will open your email composer using the address entered in the 
 <guilabel>Email:</guilabel> text box as the To: address. For example 
 <userinput>anon@example.com</userinput>.
 </para></listitem>
 
 <listitem><para>A <guilabel>File</guilabel> link cell holds the path to 
 a file or folder, as entered into the <guilabel>File location:</guilabel> 
 text box, and will try to open that file or folder with a suitable 
 application when clicked on.
 </para></listitem>
 
 <listitem><para>The <guilabel>Cell</guilabel> type of link cell holds a 
 &sheets; cell reference, entered in the <guilabel>Cell or Named Area</guilabel> text box. 
 <mousebutton>Left</mousebutton> clicking on this type of link cell causes 
 &sheets;'s focus to move to the target cell.
 </para></listitem>
 </itemizedlist>
 
 <para>All four types of link cell need some suitable text to be entered into 
 the <guilabel>Text to display</guilabel> field of the <guilabel>Insert Link</guilabel> 
 dialog. This is the text that appears in the cell.</para>
 </sect1>
 
 <sect1 id="validcheck">
 <title>Validity Checking</title>
 <para>&sheets; can automatically check the validity of entered data against 
 a number of criteria, and pop up a message box if the data is invalid.</para>
 <para>To enable this feature, select the cell(s) to be monitored and choose 
 <menuchoice><guimenu>Data</guimenu><guimenuitem>Validity...</guimenuitem>
 </menuchoice>. This will bring up &sheets;'s <guilabel>Validity</guilabel> 
 dialog box which has three tabbed pages.</para>
 <para>In the <guilabel>Criteria</guilabel> page select what type of data is to 
 be considered valid from the <guilabel>Allow:</guilabel> combo box list then 
 define the valid range of values by choosing one of the options in the 
 <guilabel>Data:</guilabel> combo box and entering suitable value(s) into 
 one or both of the edit box(es).</para>
 <para>When you have done this change to the <guilabel>Error Alert</guilabel> 
 tab. Here you can choose the type of message box
 (<guimenuitem>Stop</guimenuitem>, <guimenuitem>Warning</guimenuitem>
 or <guimenuitem>Information</guimenuitem>) that will appear when an invalid
 value is entered, and define the message box title and message text.</para>
 <!--FIXME missing Input Help tab-->
 <para>Note that this feature only checks data that you enter into the cell, 
 for a way of checking the results from formulae cells see the <link 
 linkend="formatdata">Conditional Cell Attributes</link> section of this 
 Handbook.</para>
 </sect1>
 
 <sect1 id="protection">
 <title>Protection</title>
 
 <sect2 id="doc-protection">
 <title>Document Protection</title>
 <para>Protecting the document means that without the password a user cannot add
 or delete sheets. Document protection does not protect cells.</para>
 <para>Select <menuchoice><guimenu>Tools</guimenu><guimenuitem>Protect
 Document...</guimenuitem></menuchoice>
 A dialog appears asking you for a password. The <guilabel>Password:</guilabel> strength meter
 indicates if your password is secure enough. The longer the indicator is, the
 more secure your password.</para>
 <para>
 <mediaobject>
 <imageobject>
 <imagedata fileref="cellprotection1.png" format="PNG"/>
 </imageobject>
 <textobject>
 <phrase>The Protect Document dialog</phrase>
 </textobject>
 </mediaobject>
 </para>
 <para>That password will then be required to unprotect the document.</para>
 <para>
 <mediaobject>
 <imageobject>
 <imagedata fileref="cellprotection2.png" format="PNG"/>
 </imageobject>
 <textobject>
 <phrase>The Unprotect Document dialog</phrase>
 </textobject>
 </mediaobject>
 </para>
 <para>When a document is protected, you may not:</para>
 <itemizedlist>
 <listitem><para>
 Rename a sheet
 </para></listitem>
 <listitem><para>
 Insert a sheet
 </para></listitem>
 <listitem><para>
 Remove a sheet
 </para></listitem>
 <listitem><para>
 Hide a sheet
 </para></listitem>
 <listitem><para>
 Show a sheet
 </para></listitem>
 <listitem><para>
 See the sheet properties
 </para></listitem>
 <listitem><para>
 Merge or dissociate cells
 </para></listitem>
 </itemizedlist>
 </sect2>
 
 <sect2 id="sheet-protection">
 <title>Sheet protection</title>
 <para>Protecting a sheet means protecting the contents of all protected cells
 and objects on a sheet. Individual cells or a selection of cells can be
 unprotected within a protected sheet, see <link
 linkend="cell-protection">next section</link>.</para>
 <para>To protect a sheet, select
 <menuchoice><guimenu>Tools</guimenu><guimenuitem>Protect Sheet...</guimenuitem></menuchoice>.
 A  dialog appears asking you for a password. The <guilabel>Password</guilabel> strength meter
 indicates if your password is secure enough. The longer the indicator is, the
 more secure will be your password.</para>
 <para>That password will then be required to unprotect the sheet.</para>
 <para>When a sheet is protected, you may not:</para>
 <itemizedlist>
 <listitem><para>
 Insert any object or chart
 </para></listitem>
 <listitem><para>
 Format any cell
 </para></listitem>
 <listitem><para>
 Insert a row or a column
 </para></listitem>
 <listitem><para>
 Edit and change cell content
 </para></listitem>
 <listitem><para>
 Change any content in the sheet
 </para></listitem>
 </itemizedlist>
 
 <note><para>Protecting a sheet is especially useful for preventing accidental
 erasure of formulae.</para></note>
 </sect2>
 
 <sect2 id="cell-protection">
 <title>Cell or selected cells protection</title>
 <warning><para>Cell protection is active for all cells by default and is
 effective when you enable sheet protection. So if you keep the default and if
 you protect the sheet, all cells will be protected.</para></warning>
 <para>If you want only certain cells to be protected, this default protection
 must be turned off for all other cells. For example you might  want most cells
 to accept user input so you will uncheck <guilabel>Protected</guilabel> for
 those and choose to keep protected cells that should stay unchanged (such as
 titles). So you need 3 steps in order to protect only some cells: unprotect all
 the cells, select the cells to protect and protect them and then protect the
 whole sheet.</para>
 <para>To unprotect all the cells:</para>
 <itemizedlist>
 <listitem><para>
 Select the entire spreadsheet with the mouse.
 </para></listitem>
 <listitem><para>
 In the menubar, select <menuchoice><guimenu>Format</guimenu><guimenuitem>Cell
 Format...</guimenuitem></menuchoice>. 
 </para></listitem>
 <listitem><para>
 In the dialog that appears, go to the <guilabel>Cell Protection</guilabel> tab.
 </para></listitem>
 <listitem><para>
 Check <guilabel>Hide all</guilabel> and uncheck <guilabel>Protected</guilabel>
 to remove the protection on all cells. The cells are now all unprotected.
 </para></listitem>
 </itemizedlist>
 <para>To protect a range of selected cells or a selection of non-contiguous
 cells:</para>
 <itemizedlist>
 <listitem><para>
 Highlight the range of cells that are to be protected or use the <keycombo
 action="simul">&Ctrl;</keycombo> key to select non-contiguous cells.
 </para></listitem>
 <listitem><para>
 When all of the desired cells are selected, go to
 the <menuchoice><guimenu>Format</guimenu><guimenuitem>Cell
 Format...</guimenuitem></menuchoice> menu.
 </para></listitem>
 <listitem><para>
 In the dialog that appears, go to the <guilabel>Cell Protection</guilabel> tab.
 </para></listitem>
 <listitem><para>
 Click on the box next to <guilabel>Protected</guilabel> then click
 on <guibutton>OK</guibutton>.
 </para></listitem>
 </itemizedlist>
 <para>Once the cells are marked for protection, the protection option must be
 enabled at the sheet level, that means you must protect the entire sheet for the
 cell to be effectively protected:</para>
 <itemizedlist>
 <listitem><para>
 Select
 <menuchoice><guimenu>Tools</guimenu><guimenuitem>Protect Sheet...</guimenuitem></menuchoice>.
 </para></listitem>
 <listitem><para>
 In the dialog that appears, provide a safe password, then confirm it by typing
 it again. Click on <guibutton>OK</guibutton>.
 </para></listitem>
 <listitem><para>
 Protected cells in a protected sheet cannot be edited without unprotecting the
 whole sheet, and any sheet changes are disabled. For example, no one can
 insert rows or columns, change column width, or create embedded charts. 
 </para></listitem>
 </itemizedlist>
 </sect2>
 
 <sect2 id="hide-formula">
 <title>Hide cell formula</title>
 <para>You might want to hide your formulae so other people cannot see
 them. By default, every cell is protected and not hidden. But it is important to
 remember that these attributes have no effect unless the sheet itself is
 protected.</para>
 <para>
 <mediaobject>
 <imageobject>
 <imagedata fileref="hideformula1.png" format="PNG"/>
 </imageobject>
 <textobject>
 <phrase>A default cell with a formula</phrase>
 </textobject>
 </mediaobject>
 </para>
 <para>To hide cell formulae, select the appropriate cell or range of cells or
 non-contiguous cells with <keycombo action="simul">&Ctrl;</keycombo> and
 then choose the <menuchoice><guimenu>Format</guimenu><guimenuitem>Cell
 Format...</guimenuitem></menuchoice> menu. In the Cell format
 dialog, click the <guilabel>Cell Protection</guilabel> tab and select <guilabel>Hide formula</guilabel>.
 After you protect the sheet, the results of the formulae will be visible, but
 the formulae will not. </para>
 <para>You have now to protect the sheet: choose
 <menuchoice><guimenu>Tools</guimenu><guimenuitem>Protect Sheet...</guimenuitem></menuchoice>
 to display the <guilabel>Protect Sheet</guilabel> dialog box. Enter a safe password twice to prevent
 others from unprotecting the sheet. </para>
 <para>When <guilabel>Hide formula</guilabel> is enabled and
 <guilabel>Protected</guilabel> is disabled, the formula is hidden after
 protecting the sheet but the cell content can be changed.</para>
 <para>
 <mediaobject>
 <imageobject>
 <imagedata fileref="hideformula5.png" format="PNG"/>
 </imageobject>    
 <textobject>
 <phrase><guilabel>Hide formula</guilabel> is enabled but the cell is not protected and the
 sheet is protected</phrase>
 </textobject>
 </mediaobject>
 </para>
 <para>When <guilabel>Hide formula</guilabel> and <guilabel>Protected</guilabel>
 are enabled, the formula is hidden after protecting the sheet and the cell
 content cannot be changed.</para>
 <para>
 <mediaobject>
 <imageobject>
 <imagedata fileref="hideformula2.png" format="PNG"/>
 </imageobject>
 <textobject>
 <phrase><guilabel>Hide formula</guilabel> and <guilabel>Protected</guilabel> are enabled in <guilabel>Cell Protection</guilabel> and the
 sheet is protected</phrase>
 </textobject>
 </mediaobject>
 </para>
 <para>Keep in mind that it is very easy to break the password for a
 protected sheet so if you are looking for real security, this is not the
 best solution.</para>
 </sect2>
 
 <sect2 id="hide-all">
 <title>Hide all in the cell</title>
 <para>You can hide both the formula and the content of the cell by
 choosing <guilabel>Hide all</guilabel> in the Cell Protection tab in the
 <menuchoice><guimenu>Format</guimenu><guimenuitem>Cell
 Format...</guimenuitem></menuchoice> menu. In the screenshot below, the
 cell itself is not protected (<guilabel>Protected</guilabel> is unchecked) thus
 the cell content can be changed.</para>
 <para>
 <mediaobject>
 <imageobject>
 <imagedata fileref="hideformula3.png" format="PNG"/>
 </imageobject>
 <textobject>
 <phrase><guilabel>Hide all</guilabel> only is enabled (no cell protection) and
 the sheet is protected</phrase>
 </textobject>
 </mediaobject>
 </para>
 <para>Here the cell itself is protected so it cannot be overwritten.</para>
 <para>
 <mediaobject>
 <imageobject>
 <imagedata fileref="hideformula4.png" format="PNG"/>
 </imageobject>
 <textobject>
 <phrase><guilabel>Hide all</guilabel> and <guilabel>Protected</guilabel> are
 enabled in Cell Protection and the sheet is protected</phrase>
 </textobject>
 </mediaobject>
 </para>
 </sect2>
 </sect1>
 
 
 <sect1 id="other">
 <title>Other Features</title>
 <!-- no split view in 2.4
 <sect2 id="splitview">
 <title>Splitting the View</title>
 <para>If your spreadsheet is so large that you cannot see all of it at once, 
 splitting &sheets;'s window into two or more views can help you work on it. 
 This is done by selecting <menuchoice><guimenu>View</guimenu><guimenuitem>
 Split View</guimenuitem></menuchoice> which will split the current view into 
 two parts. <menuchoice><guimenu>View</guimenu><guisubmenu>Splitter Orientation
 </guisubmenu></menuchoice> lets you choose between 
 <guimenuitem>Horizontal</guimenuitem> and <guimenuitem>Vertical</guimenuitem> 
 splitting.</para>
 <para>This technique is particularly useful when you want to select an area 
 of the spreadsheet that is larger than can be shown in one view, perhaps to
 paste a copied cell into it. 
 Use the scrollbars to position the two views to show the top left and 
 bottom right cells of the wanted area, select the top left cell in one 
 view then hold the &Shift; key pressed while you select the 
 bottom right cell with the <mousebutton>left</mousebutton> mouse button.</para>
 <para>If there is more than one sheet in your document, you can show a 
 different sheet in each of the split views.</para>
 <para>The relative sizes of the views can be changed by dragging the thick bar 
 separating the views.</para>
 <para>To remove a view select <menuchoice><guimenu>View</guimenu><guimenuitem>
 Remove View</guimenuitem></menuchoice></para>
 </sect2>
 -->
 
 <sect2 id="namedareas">
 <title>Named Cells and Areas</title>
 <para>You can give a name such as <userinput>foo</userinput> to a cell or to 
 any area of a sheet by selecting the cell or area then selecting <guimenuitem>
 Area Name...</guimenuitem> from the <mousebutton>right</mousebutton> mouse 
 button menu. This will bring up the <guilabel>Area Name</guilabel> dialog box 
 where you can enter any name you wish.</para>
 <para>You can also name a cell or area by selecting it then typing the name 
 into the small text box at the left end of the Formula toolbar, overwriting the 
 cell reference that normally appears here.</para>
 <para>If you enter a name that has already been used into this text box 
 &sheets;'s selection will change to show the named cell(s).</para>
 <para>The <menuchoice><guimenu>Data</guimenu><guimenuitem>Named Areas...</guimenuitem>
 </menuchoice> option will give you a list of existing names 
 and let you change &sheets;'s focus to any of them or let you remove a name.
 </para>
 <para>Named cells are particularly useful in formulae as an alternative to 
 <link linkend="absolute"> absolute cell references</link> as the names can 
 be used in place of normal cell references and do not change when the 
 cell containing the formula is copied. When a name is used in this way it
 should be enclosed in single quotation marks.</para>
 <para>For example, if cell A1 has been given the name <userinput>fred
 </userinput> then you can enter a formula such as <userinput>='fred' + 2
 </userinput> into another cell which would always give the result of adding 
 2 to the value in A1 no matter where the formula cell was copied to.</para>
 <para>Note that cell and area names are treated as being in lowercase.</para>
 </sect2>
 
 <sect2 id="cellcomments">
 <title>Cell Comments</title>
 <para>A cell can contain a text comment that can be viewed when working on 
 the spreadsheet but which is not printed and not normally seen.</para>
 <para>To add a comment select the cell and choose <guimenuitem>Comment...</guimenuitem> 
 from the <mousebutton>right</mousebutton> mouse 
 button menu or from the <guimenu>Insert</guimenu> menu and type your comment into the 
 resulting <guilabel>Cell Comment</guilabel> dialog box.</para>
 <para>To see the comment hover the mouse pointer over  
 the cell. The comment will appear as if it were a Tooltip.
 </para>
 <para>If you check the <guilabel>Show comment indicator</guilabel> box of the 
 <guilabel>Sheet Properties</guilabel> dialog, those 
 cells containing comments will be highlighted by a small red triangle in the 
 top right corner.</para>
 <para>To open this dialog, click with the <mousebutton>right</mousebutton> mouse 
 button onto the sheet tab at the bottom of the main window and select 
 <guimenuitem>Sheet Properties</guimenuitem> from the popup menu. Or select it from the 
 <menuchoice><guimenu>Format</guimenu><guisubmenu>Sheet</guisubmenu></menuchoice> menu.</para>
 
 <para>To remove a comment from a cell, select <guimenuitem>Remove Comment</guimenuitem> 
 from the <mousebutton>right</mousebutton> mouse button menu or 
 choose <menuchoice><guimenu>Edit</guimenu><guisubmenu>Clear</guisubmenu>
 <guimenuitem>Comment</guimenuitem></menuchoice>.</para>
 </sect2>
 
 </sect1>
 
 </chapter>
 
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