| Re: Can anyone show me how to do this without loops? [message #4766] |
Mon, 31 July 1995 00:00 |
chase
Messages: 62
Registered: May 1993
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>>>> > "Liam" == Liam Gumley <liamg@ssec.wisc.edu> writes:
In article <3vilva$5uq@spool.cs.wisc.edu> Liam Gumley <liamg@ssec.wisc.edu> writes:
Liam> Can anyone show me how to code this algorithm without loops?
Liam> Data types are:
Liam> degree is an integer
Liam> i = degree + 1
Liam> j = degree + 1
Liam> kx = fltarr( i, j ) ; contains polynomial coefficients
Liam> ky = fltarr( i, j ) ; contains polynomial coefficients
Liam> x0, y0, xi, yi are float variables or vectors
Liam> Here is the code:
Liam> xi = 0.0
Liam> yi = 0.0
Liam> for i = 0, degree do begin
Liam> for j = 0, degree do begin
Liam> xi = xi + kx( i, j ) * x0 ^ j * y0 ^ i
Liam> yi = yi + ky( i, j ) * x0 ^ j * y0 ^ i
Liam> endfor
Liam> endfor
Try this:
x = x0^indgen(degree+1) ; Unfortunately IDL does not have a recursive
y = y0^indgen(degree+1) ; filter operator (AR) to efficiently do this.
xi = y # (kx # x)
yi = y # (ky # x)
Chris
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