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Re: Daily to monthly [message #89897 is a reply to message #89888]

Fri, 19 December 2014 01:31

lecacheux.alain
Messages: 325
Registered: January 2008

Senior Member

On Wednesday, December 17, 2014 9:54:17 PM UTC+1, Craig Markwardt wrote:
> On Tuesday, December 16, 2014 1:21:46 PM UTC-5, mani...@gmail.com wrote:
>> Hi Craig,
>> I need Monthly means where missing values are taken care of
>
> Average = sum / n_points
>
> The only trick is that n_points could be different depending on missing data. So if I had an array of values DATA[*,*] where DATA[i,j] is the ith position on the jth day, and missing value is -999, I could sum them like this,
>
> tot = 0 ;; cumulative sum of data values
> npt = 0 ;; cumulative sum of number of good data values
> for j = 0, NDAYS-1 do begin
> mask = data[*,j] NE -999 ;; mask of good values only, 1=good
> npt = npt + mask ;; add to number of good values
> tot = tot + (data[*,j]*mask) ;; add good vals to cumulative data sum
> endfor
>
> ;; Compute average
> av = tot / npt
>
> Craig

Hi Craig,
Note that you might simply do:
mask = data ne -999
av = Total(data*mask, 2)/Total(mask, 2); daily average
av = Total(data*mask)/Total(mask); overall average
etc...

alx.

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[Message index]

		Daily to monthly By: manikbali on Mon, 15 December 2014 20:10
		Re: Daily to monthly By: Craig Markwardt on Tue, 16 December 2014 09:49
		Re: Daily to monthly By: manikbali on Tue, 16 December 2014 10:21
		Re: Daily to monthly By: Craig Markwardt on Wed, 17 December 2014 12:54
		Re: Daily to monthly By: lecacheux.alain on Fri, 19 December 2014 01:31

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