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Re: Maximum Intensity without FOR Loop [message #39402]

Tue, 11 May 2004 12:46

btt
Messages: 345
Registered: December 2000

Senior Member

Stefan Tuchschmid wrote:
> Hi there
> a lot of posts talk about the necessity to avoid FOR loops ('if you
> use for loops, make sure a lot of stuff is happening in there...').
> However, I can't seem to find a better & working solution for the
> following code fragment:
>
> FOR i=0,x_resolution-1 DO BEGIN
> FOR j=0,y_resolution-1 DO BEGIN
> reformat_data[i,j,k]=MAX(data[i,j,lower_limit:upper_limit])
> ENDFOR
> ENDFOR
>
> Background: data is a image stack (MRI 3D Data), we would like to find
> the MIP (Maximum Intesity Projection) over a certain number of images.

Hi,

IDL> data = Bindgen(3,4,5)

You could use the DIMENSION keyword to MAX to find the maximum in that
dimension (across the entire array.)

IDL> print, max(data, dim = 3)
48 49 50
51 52 53
54 55 56
57 58 59

Or, you could find the maximum using the 'max' operator on specified
dismension (you can do more than two at a time.)

IDL> print, data[*,*,0] > data[*,*,2]
24 25 26
27 28 29
30 31 32
33 34 35

Ben

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		Re: Maximum Intensity without FOR Loop By: btt on Tue, 11 May 2004 12:46
		Re: Maximum Intensity without FOR Loop By: David Fanning on Tue, 11 May 2004 12:29

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