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Last Post 28 Nov 2006 08:23 AM by  anon
deriv function and interfile images
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anon



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28 Nov 2006 08:23 AM
    I have 2 questions, does anyone know mathematically what the deriv funciton actually does when used for 2D arrays? help says it performs a numerical differentiation using a 3 point langrangian interpolation... how does that work in 2D also is there a simple way to convert from interfile images to dicoms or read interfile files to a 2D array? cheers.

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    28 Nov 2006 08:23 AM
    The DERIV function treats a 2-dimensional array as a vector - Reading left to right and top to bottom. Consider the following: IDL> x = findgen(16) IDL> y = randomu(seed,16) IDL> print, deriv(x,y) % Compiled module: DERIV. 0.173069 0.0833770 0.0859829 -0.181817 0.139804 0.256416 -0.341754 0.00444040 0.205324 -0.266507 0.0295178 0.392275 -0.291976 -0.398254 0.0532303 0.164015 IDL> x = reform(x,4,4) & y = reform(y,4,4) IDL> print, deriv(x,y) 0.173069 0.0833770 0.0859829 -0.181817 0.139804 0.256416 -0.341754 0.00444040 0.205324 -0.266507 0.0295178 0.392275 -0.291976 -0.398254 0.0532303 0.164015 IDL>
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