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arithmetic operation on array [message #85477]

Mon, 12 August 2013 13:59

Phillip Miller
Messages: 4
Registered: August 2013

Junior Member

Possibly a dumb question, but I'm pretty new to IDL:

I have a geographically explicit time-series with 456 time steps and a
1 degree resolution, so an array of dimensions 360 x 180 x 456, and I
would like to recalculate it as the anomaly from the time-series
average.

I can calculate the time series average no problem

> average = mean(data, dimension=3)

But, of course, when I try

> anomaly = data - mean(data, dimension=3)

then I "lose" my third dimension, and end up with an array of 360 x
180, rather than what I want, which is an array that is the same size
as my original.

I know that I could loop it like

> for i = 0,456 data[*,*,i] = data[*,*,i] - mean(data, dimension=3)

but I feel like there must be a better way than making a for loop. Am
I supposed to duplicate mean(data, dimension=3) times 456 in order to
create an identically sized array for the minus operation? (i.e., an
array with dimensions 360 x 180 x 456, but where each of the 456
"slices" is identical)

Thanks in advance for any suggestions!

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[Message index]

		arithmetic operation on array By: Phillip Miller on Mon, 12 August 2013 13:59
		Re: arithmetic operation on array By: David Fanning on Mon, 12 August 2013 14:24
		Re: arithmetic operation on array By: Phillip Bitzer on Mon, 12 August 2013 15:22
		Re: arithmetic operation on array By: Phillip Miller on Mon, 12 August 2013 16:08
		Re: arithmetic operation on array By: Phillip Miller on Mon, 12 August 2013 16:17
		Re: arithmetic operation on array By: David Fanning on Mon, 12 August 2013 16:18
		Re: arithmetic operation on array By: Phillip Bitzer on Mon, 12 August 2013 16:37
		Re: arithmetic operation on array By: Phillip Miller on Mon, 12 August 2013 15:51
		Re: arithmetic operation on array By: John Correira on Wed, 14 August 2013 12:24
		Re: arithmetic operation on array By: wlandsman on Wed, 14 August 2013 12:54

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