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Re: Can this be done using array operations instead? [message #66104 is a reply to message #65921]

Thu, 02 April 2009 12:43

robintw
Messages: 37
Registered: March 2009

Member

Thank you everyone for your help. I've now managed to write a function
to do this with array functions. I've put the code below if anyone is
interested. I realised that all I really needed was the sum of the
values, and I could do all the rest by arithmetic operations on the
array itself.

However, the next part of this project will require using subarrays as
I will need to get the Standard Deviation of each 3x3 square. Is there
a way to do this?

Cheers,

Robin

Code Here:

; Creates a Getis image given a FID, the dimensions of the file, a
distance to use for the getis routine
; and a base window to send progress updates to
PRO CREATE_GETIS_IMAGE, file, dims, distance, report_base
; TODO: Get this to loop through bands
; Get the data for the first band of the file (ignores pos from
earlier)
WholeBand = ENVI_GET_DATA(fid=file, dims=dims, pos=0)

; Calculate the dimensions of WholeBand
SizeInfo = SIZE(WholeBand, /DIMENSIONS)
NumRows = SizeInfo[0]
NumCols = SizeInfo[1]

; Get the global mean
GlobMean = MEAN(WholeBand)

; Get the global variance
GlobVariance = VARIANCE(WholeBand)

; Get the number of values in the whole image
GlobNumber = NumRows * NumCols

DimOfArray = (distance * 2) + 1
Kernel = FLTARR(DimOfArray, DimOfArray)
Kernel = Kernel + 1
print, Kernel
SummedImage = CONVOL(FLOAT(WholeBand), Kernel, /CENTER, /EDGE_ZERO)

TopFraction = SummedImage - (FLOAT(9) * GlobMean)

SquareRootAnswer = SQRT((FLOAT(9) * (GlobNumber - 9))/(GlobNumber -
1))
BottomFraction = GlobVariance * SquareRootAnswer

Getis = FLOAT(TopFraction) / BottomFraction

ENVI_ENTER_DATA, Getis

print, "Program finished."
END

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[Message index]

		Can this be done using array operations instead? By: robintw on Thu, 02 April 2009 07:34
		Re: Can this be done using array operations instead? By: Jeremy Bailin on Thu, 02 April 2009 14:11
		Re: Can this be done using array operations instead? By: robintw on Thu, 02 April 2009 12:43
		Re: Can this be done using array operations instead? By: robintw on Thu, 02 April 2009 11:58
		Re: Can this be done using array operations instead? By: Jean H. on Thu, 02 April 2009 11:39
		Re: Can this be done using array operations instead? By: robintw on Thu, 02 April 2009 10:38
		Re: Can this be done using array operations instead? By: Allan Whiteford on Thu, 02 April 2009 10:16
		Re: Can this be done using array operations instead? By: robintw on Thu, 02 April 2009 09:26
		Re: Can this be done using array operations instead? By: Juggernaut on Thu, 02 April 2009 08:58

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