Standard deviation in BIRT

Tim Winselmann

Hey there,

i am trying to calculate the standard deviation of three values within the Aggregation Builder via Function STDDEV. This works great - except the case that the three values are all equal (like 3.2, 3.2, 3.2) than the standard deviation is "NaN" (which maybe stands for 'Not a Number'?) and not the correct value "0".

I have attached a very small version of my report, which just shows this behavior. Can somebody look over this to insure that i do not make a mistake or to confirm that this behavior could be a bug in the BIRT implementation of standard deviation?

I'm working with the BIRT Designer 2.6.2.

Thanks so far,
Tim

PS: I can't upload the file, there is an "Error This upload failed" Message It seems like a can't attach the rptdesign-file, but other files are working? What else could i try?

Tim Winselmann

I do not find a nicer way to attach my rptdesign example, so i decided to post it as a code "snippet"... <br />
<br />
<pre class='_prettyXprint _lang-auto _linenums:0'>
<?xml version="1.0" encoding="UTF-8"?>
<report xmlns="http://www.eclipse.org/birt/2005/design" version="3.2.22" id="1">
<property name="comments">Copyright (c) 2007 &lt;&lt;Your Company Name here>></property>
<property name="createdBy">Eclipse BIRT Designer Version 2.6.2.r262_v20110209 Build &lt;2.6.2.v20110219-1842></property>
<html-property name="description">Creates a blank report with no predefined content.</html-property>
<property name="units">in</property>
<text-property name="displayName">Blank Report</text-property>
<property name="iconFile">/templates/blank_report.gif</property>
<property name="layoutPreference">auto layout</property>
<data-sources>
<script-data-source name="Data Source1" id="13"/>
</data-sources>
<data-sets>
<script-data-set name="Data Set1" id="14">
<list-property name="resultSetHints">
<structure>
<property name="position">1</property>
<property name="name">val</property>
<property name="dataType">float</property>
</structure>
</list-property>
<list-property name="columnHints">
<structure>
<property name="columnName">val</property>
</structure>
</list-property>
<structure name="cachedMetaData">
<list-property name="resultSet">
<structure>
<property name="position">1</property>
<property name="name">val</property>
<property name="dataType">float</property>
</structure>
</list-property>
</structure>
<property name="dataSource">Data Source1</property>
<method name="open"><![CDATA[i = 0;

sourcedata = new Array( new Array(2),
new Array(2),
new Array(2));
sourcedata[0][0] = "Keyboard";
sourcedata[0][1] = 25.63;

sourcedata[1][0] = "Mouse";
sourcedata[1][1] = 25.63;

sourcedata[2][0] = "Memory";
sourcedata[2][1] = 25.63;
]]></method>
<method name="fetch"><![CDATA[if ( i < 3 )
{
row["cat"] = sourcedata[i][0];
row["val"] = sourcedata[i][1];
i++;
return true;
}
return false;]]></method>
</script-data-set>
</data-sets>
<styles>
<style name="crosstab" id="4">
<property name="borderBottomColor">#CCCCCC</property>
<property name="borderBottomStyle">solid</property>
<property name="borderBottomWidth">1pt</property>
<property name="borderLeftColor">#CCCCCC</property>
<property name="borderLeftStyle">solid</property>
<property name="borderLeftWidth">1pt</property>
<property name="borderRightColor">#CCCCCC</property>
<property name="borderRightStyle">solid</property>
<property name="borderRightWidth">1pt</property>
<property name="borderTopColor">#CCCCCC</property>
<property name="borderTopStyle">solid</property>
<property name="borderTopWidth">1pt</property>
</style>
<style name="crosstab-cell" id="5">
<property name="borderBottomColor">#CCCCCC</property>
<property name="borderBottomStyle">solid</property>
<property name="borderBottomWidth">1pt</property>
<property name="borderLeftColor">#CCCCCC</property>
<property name="borderLeftStyle">solid</property>
<property name="borderLeftWidth">1pt</property>
<property name="borderRightColor">#CCCCCC</property>
<property name="borderRightStyle">solid</property>
<property name="borderRightWidth">1pt</property>
<property name="borderTopColor">#CCCCCC</property>
<property name="borderTopStyle">solid</property>
<property name="borderTopWidth">1pt</property>
</style>
</styles>
<page-setup>
<simple-master-page name="NewSimpleMasterPage" id="12">
<property name="topMargin">1in</property>
<property name="leftMargin">1.25in</property>
<property name="bottomMargin">1in</property>
<property name="rightMargin">1.25in</property>
</simple-master-page>
</page-setup>
<body>
<table id="19">
<property name="dataSet">Data Set1</property>
<list-property name="boundDataColumns">
<structure>
<property name="name">val</property>
<text-property name="displayName">val</text-property>
<expression name="expression" type="javascript">dataSetRow["val"]</expression>
<property name="dataType">float</property>
</structure>
<structure>
<property name="name">Aggregation</property>
<property name="dataType">float</property>
<property name="aggregateFunction">STDDEV</property>
<list-property name="arguments">
<structure>
<property name="name">Expression</property>
<expression name="value" type="javascript">row["val"]</expression>
</structure>
</list-property>
</structure>
<structure>
<property name="name">Column Binding</property>
<expression name="expression" type="javascript">dataSetRow["val"]</expression>
<property name="dataType">string</property>
</structure>
</list-property>
<column id="32">
<property name="width">1.4479166666666667in</property>
</column>
<column id="26">
<property name="width">4.5in</property>
</column>
<header>
<row id="20">
<cell id="29"/>
<cell id="21"/>
</row>
</header>
<detail>
<row id="22">
<cell id="30">
<label id="34">
<text-property name="text">Value:</text-property>
</label>
</cell>
<cell id="23">
<data id="28">
<property name="resultSetColumn">Column Binding</property>
</data>
</cell>
</row>
</detail>
<footer>
<row id="24">
<cell id="31">
<label id="35">
<text-property name="text">Standard Deviation</text-property>
</label>
</cell>
<cell id="25">
<data id="27">
<structure name="numberFormat">
<property name="category">Custom</property>
</structure>
<property name="resultSetColumn">Aggregation</property>
</data>
</cell>
</row>
</footer>
</table>
</body>
</report>

</pre>