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Line of best fit for bar charts

akshatha_k

Hi,

I have to generate a 'Line of best fit' for a Bar/line chart. And i have x-axis values as string and y-axis values as number(int). Also, my BIRT version is 2.6.1. Please help me out.

Thanks in Advance,
Akshatha

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mwilliams

Have you seen this post, in the devShare?

http://www.birt-exchange.org/org/devshare/designing-birt-reports/1548-creating-a-line-of-best-fit-line-in-a-scatter-chart/

akshatha_k

Hi, 
 
Thanks a lot for the quick reply. 
 
Yes, i have looked into that link. But, in that case we have x-axis values as float. I have my x-axis value as a string. Can you help me modify the same for my requirement? 
 
Also, my BIRT version is 2.6.1 
 
Regards, 
Akshatha

mwilliams

Take a look at this modified report. I created it in BIRT 2.6.1. Rather than dealing with the x-axis value, we just deal with the x-axis value index to create the slope of the line.

akshatha_k

Hi, 
 
Thank you for your reply again. The report design is working perfectly fine for my requirement but,with one exception. 
 
Suppose if the y-axis value is null, the "Line of best Fit" is not generating. 
 
I'm attaching the modified report design in which there is a second chart which depicts this scenario. Please find the attachment for the same. 
 
Waiting for you reply. 
 
Regards, 
Akshatha

mwilliams

Can you try attaching again? When I try to open the attached file, I get told it has errors that keep it from being opened.

akshatha_k

Hi,

Please find the attachment.

Regards,
Akshatha

mwilliams

Just add a simple check for null values when adding up the y-series values: 
 
<pre class='_prettyXprint _lang-auto _linenums:0'>
if(series.getSeriesIdentifier() == "ValueSeries2"){
yvals = dataSet.getValues();
//find first half average y point
for(i=0;i<numFirstHalfValues;i++){
if(yvals[i] != null){
firstHalfYTotal = firstHalfYTotal + parseFloat(yvals[i]);
}
}
firstHalfAvgY = firstHalfYTotal / numFirstHalfValues;

//find second half average y point
for(i=numFirstHalfValues;i<numValues;i++){
if(yvals[i] != null){
secondHalfYTotal = secondHalfYTotal + parseFloat(yvals[i]);
}
}
secondHalfAvgY = secondHalfYTotal / numSecondHalfValues;
}
</pre>
 
Hope this helps.

akshatha_k

Hi,

That worked perfectly. Thank you for your help.

Regards,
Akshatha

mwilliams

You're welcome! Let me know if you run into any more problems, with this.