On Jan 26, 4:56 pm, Jeremy Bailin <astroco...@gmail.com> wrote:
> On Jan 25, 7:49 pm, Ed Hyer <ejh...@gmail.com> wrote:
>
>
>
>
>
>> On Jan 25, 12:47 pm, Ed Hyer <ejh...@gmail.com> wrote:
>
>>> 1) The number of different values in the matched grids;
>>> 2) The mode, that is, the frequency of the most common value.
>
>> So, what I ended up with was something like this:
>
>> allgrids=[[[grid1]],[[grid2]],etc.]
>> matchcount=allgrids *0b; initialize
>> for i1=0,ngrids-1 do for i2=0,ngrids-1 do matchcount[*,*,i1] +=
>> (allgrids[*,*,i1] eq allgrids[*,*,i2])
>> magnitude_of_mode = max(matchcount,dim=3,imode)
>> value_of_mode = allgrids[imode]
>
>> So 2 for-loops still needed, but across the shortest dimension.
>
>> --Edward H.
>
> Here's a pure IDL no-loop solution that uses... <drum roll>... the
> combination of VALUE_LOCATE and HISTOGRAM! (tell me you didn't see
> that coming).
>
> ; some sample data
> grid1 = [[1., 0, -10, 1.],[-5, -10, 9, 8],[0, 1, 2, 3]]
> grid2 = [[1., 9, 8, 2],[-5, 0, 2, 3],[0, 1, 2, 3]]
> grid3 = [[-10, 8, 9, 2],[-5, -10, 1, 3],[0, 1, 2, 3]]
> grid4 = [[0, 9, 8, 2],[-10, 2, 2, 2],[0, 1, 2, 3]]
> grid5 = [[1., -2, -20, 2],[-5, 2, 2, 8],[0, 1, 2, 3]]
>
> allgrids = [[[grid1]],[[grid2]],[[grid3]],[[grid4]],[[grid5]]]
>
> gridsize=size(allgrids,/dimen)
> npix = gridsize[0]*gridsize[1]
> uniqvals = allgrids[uniq(allgrids,sort(allgrids))]
> nuniq = n_elements(uniqvals)
> ; map values into their index in uniqvals so we only need to
> ; deal with integers
> mappedgrids = value_locate(uniqvals, allgrids)
> ; now we can use histogram!
> ; first give each pixel its own increment so that the histogram for
> ; the pixels run from 0..nuniq-1, nuniq..2*nuniq-1, etc.
> pixincrement = ((lindgen(gridsize[0]) # replicate(1,gridsize[1])) + $
> (lindgen(gridsize[1]) ## replicate(1,gridsize[0]) * gridsize[0])) *
> nuniq
> ; now histogram everything
> gridhist = reform(histogram(mappedgrids + rebin
> (pixincrement,gridsize), $
> bin=1, min=0, max=npix*nuniq-1), nuniq, gridsize[0], gridsize[1])
>
> ; get the mode and value out of the histogram, for each pixel
> magnitude_of_mode = max(gridhist, dim=1, imode)
> value_of_mode = uniqvals[imode - pixincrement]
>
> IDL> print, magnitude_of_mode
> 3 2 2 4
> 4 2 3 2
> 5 5 5 5
> IDL> print, value_of_mode
> 1.00000 9.00000 8.00000 2.00000
> -5.00000 -10.0000 2.00000 3.00000
> 0.00000 1.00000 2.00000 3.00000
>
> -Jeremy.
Oh, and I almost forgot your first requirement: the number of
different values at each pixel:
variation_of_cells = total(gridhist gt 0, 1, /int)
IDL> print, variation_of_cells
3 4 4 2
2 3 3 3
1 1 1 1
-Jeremy.
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