topic Re: Issue calculating standard deviation in QlikView

Issue calculating standard deviation

jarrad_murray — Wed, 03 Aug 2016 15:29:11 GMT

Hi All,

I am having an issue with calculating a standard deviation from a record level table.

I have a table with the following aggregated values 243, 309, 452, ,587, ,580, ,447, ,540, ,560, ,518, ,565, ,584, ,613, ,462, ,455. Performing a standard deviation calucation on this gives me a figure of 108.89

Using the code '=Stdev(aggr(sum({<PODGroup4Description = {'AandE'}>}ActivityActual), MonthYear))' gives me the figure 262.76

Has anyone encountered this before or does anyone have an idea as to what I am doing wrong.

Any help is greatly appreciated.

Re: Issue calculating standard deviation

Clever_Anjos — Wed, 03 Aug 2016 16:09:14 GMT

If you need to agregate that table, you´re using a AGGR() as an expression

Re: Issue calculating standard deviation

Clever_Anjos — Wed, 03 Aug 2016 16:14:46 GMT

Usefull reading: Pitfalls of the Aggr function

Re: Issue calculating standard deviation

Anil_Babu_Samineni — Wed, 03 Aug 2016 16:23:48 GMT

Perhaps This?

=Stdev(aggr(sum({<PODGroup4Description = {'AandE'}>}ActivityActual), MonthYear, ActivityActual))

Re: Issue calculating standard deviation

Frank_Hartmann — Wed, 03 Aug 2016 16:32:09 GMT

I think the problem is that you dont set a Filter on MonthYear.

In your Textbox expression the Stdev is accounted for all the values in Field "MonthYear".

But the values you are showing in chart are restricted in MonthYear . So just set a Filter in Month Year as shown in attached sample or use SetAnalysis for filtering in MonthYear.

hope this helps

Re: Issue calculating standard deviation

jarrad_murray — Thu, 04 Aug 2016 08:35:47 GMT

Hi Frank,

This is fantastic. I didn't think the non available months would play a part in this.

Thank you very much.