[gnumeric] add example on using array functions to replace database functions

[Andreas J. Guelzow <guelzow src gnome org>]

commit cf1385c91f80ef76df3af76bae0538cb379a0bc4
Author: Andreas J Guelzow <aguelzow pyrshep ca>
Date:   Thu Dec 1 14:11:25 2011 -0700

    add example on using array functions to replace database functions
    
    2011-12-01  Andreas J. Guelzow <aguelzow pyrshep ca>
    
    	* data-types.xml: update
    	* figures/Makefile.am: add formula-dmedian.png
    	* figures/formula-dmedian.png: new

 doc/C/ChangeLog                   |    6 ++++
 doc/C/data-types.xml              |   53 +++++++++++++++++++++++++++++++++++++
 doc/C/figures/Makefile.am         |    1 +
 doc/C/figures/formula-dmedian.png |  Bin 0 -> 29206 bytes
 4 files changed, 60 insertions(+), 0 deletions(-)
---
diff --git a/doc/C/ChangeLog b/doc/C/ChangeLog
index f2347ba..507b0d6 100644
--- a/doc/C/ChangeLog
+++ b/doc/C/ChangeLog
@@ -1,3 +1,9 @@
+2011-12-01  Andreas J. Guelzow <aguelzow pyrshep ca>
+
+	* data-types.xml: update
+	* figures/Makefile.am: add formula-dmedian.png
+	* figures/formula-dmedian.png: new
+
 2011-11-30  Andreas J. Guelzow <aguelzow pyrshep ca>
 
 	* data-types.xml: update
diff --git a/doc/C/data-types.xml b/doc/C/data-types.xml
index 652c07e..bf426cf 100644
--- a/doc/C/data-types.xml
+++ b/doc/C/data-types.xml
@@ -837,6 +837,59 @@ FUNCTIONNAME(ARGUMENTS)
 
   </sect3>
 
+  <sect3 id="sect-data-formulas-database">
+    <title>Database Formulas</title>
+  <para>
+    Solely for compatibility with Excel and ODF files, &gnum; supports various database functions:
+    <xref linkend="gnumeric-function-DAVERAGE" />,
+    <xref linkend="gnumeric-function-DCOUNT" />,
+    <xref linkend="gnumeric-function-DCOUNTA" />,
+    <xref linkend="gnumeric-function-DGET" />,
+    <xref linkend="gnumeric-function-DMAX" />,
+    <xref linkend="gnumeric-function-DMIN" />,
+    <xref linkend="gnumeric-function-DPRODUCT" />,
+    <xref linkend="gnumeric-function-DSTDEV" />,
+    <xref linkend="gnumeric-function-DSTDEVP" />,
+    <xref linkend="gnumeric-function-DSUM" />,
+    <xref linkend="gnumeric-function-DVAR" /> and
+    <xref linkend="gnumeric-function-DVARP" />.
+  </para>
+  <para>
+    Since these functions are quite restrictive on the criteria that can be used, it is often
+    easier to use array functions as described in <xref linkend="sect-data-formulas-array" />.
+    Array functions are also useful in the case that a specific database function does not exist:
+  </para>
+
+ <example id="dmedian">
+   <title>Simulating <code>DMEDIAN</code> with an Array Function</title>
+   <para>
+     As shown in  <xref linkend="dmedian-example-1" />, instead of using (the non-existing) 
+     function <code>DMEDIAN</code> one can use the alternative expression 
+     <code>median(if(A1:A20="AA",B1:B2))</code> entered as an array function as described in 
+     <xref linkend="sect-data-formulas-array" />. Multiple conditions can be combined using
+     the <code>AND</code> or <code>OR</code> functions as in 
+     <code>median(if(OR(A1:A20="AA",A1:A20="BB"),B1:B20))</code>.
+     Using defined names as introduced in <xref linkend="sect-data-formulas-names" /> for 
+     <code>A1:A20</code> and <code>B1:B20</code> can make this code very flexible and readable.
+   </para> 
+ </example>
+  
+  <figure id="dmedian-example-1">
+    <title>Calculating the MEDIAN of Some Data Values</title>
+    <screenshot>
+	<mediaobject>
+            <imageobject>
+              <imagedata fileref="figures/formula-dmedian.png" 
+                  format="PNG" />
+            </imageobject>
+            <textobject>
+              <phrase>Calculating the MEDIAN of some data values.</phrase>
+            </textobject>
+           </mediaobject>
+    </screenshot>
+  </figure>
+
+ </sect3>
 
 </sect2>
              
diff --git a/doc/C/figures/Makefile.am b/doc/C/figures/Makefile.am
index 6966b96..b1c68fd 100644
--- a/doc/C/figures/Makefile.am
+++ b/doc/C/figures/Makefile.am
@@ -227,6 +227,7 @@ EXTRA_DIST = \
      files-html-example.png \
      files-html32-example.png \
      files-html40-example.png \
+     formula-dmedian.png \
      gnumeric-icon-24.png \
      gnumeric-labelled.png \
      gnumeric-power-example.png \
diff --git a/doc/C/figures/formula-dmedian.png b/doc/C/figures/formula-dmedian.png
new file mode 100644
index 0000000..bf29d08
Binary files /dev/null and b/doc/C/figures/formula-dmedian.png differ