Neep help writing a formula that can find an unknown range in a column

[Peter h]

I need to find the standard deviation of data from the previous month. So, in column "A" I have dates, and column "B" I have my data. Data is being added multiple times a day. So then I have my cell that shows the standard deviation in Cell C1. How would I write the formula to only show the standard deviation of the previous month based on the dates entered in column "A"? So for instance, right now I need to see the standard deviation of the data that was entered in November. Thanks.

 

[Tetra201]

See if the following array formula (to be entered using Ctrl+Shift+Enter, not just Enter) works for you:

=STDEV(IF((A2:A10000 > EOMONTH(TODAY(),-2))*(A2:A10000 < EOMONTH(TODAY(),-1)+1),B2:B10000))<eomonth(today(),-1)+1),b2:b10000))< html=""></eomonth(today(),-1)+1),b2:b10000))<>

 

[Peter h]

See if the following array formula (to be entered using Ctrl+Shift+Enter, not just Enter) works for you:

=STDEV(IF((A2:A10000 > EOMONTH(TODAY(),-2))*(A2:A10000 < EOMONTH(TODAY(),-1)+1),B2:B10000))<eomonth(today(),-1)+1),b2:b10000))< html=""></eomonth(today(),-1)+1),b2:b10000))<>

That worked like a charm. Thank you very much.

 

[Tetra201]

Glad to have helped.