| collapsing 3-d arrays [message #6505] |
Wed, 10 July 1996 00:00  |
deb
Messages: 12
Registered: April 1996
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Junior Member |
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I have a pretty large 3-D data array (~10 million pts). I'd like to
collapse
the data and look at a 2-d image that contains the max value encountered
along the third coordinate. I can write a nested loop that
looks thru the array and pulls out the max data value along the z-axis
for each
x,y coordinate pair, but that's pretty cumbersome. It seems like IDL
should have
a built-in function for doing this kind of thing, but i can't seem to
find it.
The project_vol command looks like it might do what i want but i can't
seem to
convince it to give projections along the (x,y), (x,z) and/or (y,z)
planes..it
does some weird pseudo-isometric thing. Does anyone have any hints on
how to
accomplish this efficiently within IDL?
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| Re: collapsing 3-d arrays [message #6584 is a reply to message #6505] |
Thu, 11 July 1996 00:00  |
hahn
Messages: 108
Registered: November 1993
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Senior Member |
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deb <summa@lanl.gov> wrote:
> I have a pretty large 3-D data array (~10 million pts). I'd like to
> collapse
> the data and look at a 2-d image that contains the max value encountered
> along the third coordinate. I can write a nested loop that
> looks thru the array and pulls out the max data value along the z-axis
> for each
> x,y coordinate pair, but that's pretty cumbersome. It seems like IDL
> should have
> a built-in function for doing this kind of thing, but i can't seem to
> find it.
The IDL function is MAX. It accepts an array as argument and returns
a scalar. Thus you need two nested loops to make a 2-d matrix.
Let's assume your 3-D data array is named D3, you may write:
si = size ( D3 )
D2 = fltarr(si(1),si(2), /nozero)
for i=0,si(1)-1 do begin
for j=0,si(2)-1 do D2(i,j) = max ( D3(i,j,*) )
endfor
Hope this helps
Norbert
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