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function of two variables [message #1894]

Thu, 17 March 1994 12:55

brooker
Messages: 12
Registered: March 1994

Junior Member

Hello from Canada!!

I have the following IDL question:

Assume I have the functions Y=2.*X + 3. and I want to plot Y vs X over the
range [0,10]

I could code this as

X=findgen(101)/100.*10.
Y=2.*X + 3.
plot,x,y

Very nice!! Only array operations. NO LOOPING!!!!!! Very FAST!!!!!

But what if now I had Z=2.*X + 3.*Y and I want to plot Z as X and Y both
range from 0 to 10. A way to code this is

X=findgen(101)/100.*10.
Y=X
num_y=n_elements(Y)
num_x=n_elements(X)
z=fltarr(num_x,num_y)
for j=0,numy-1 do begin
z(*,j)=2.*X + 3.*Y(j)
endfor
surface,Z,X,Y

Very inefficient because of the loop!! Very slow!!

Is there anyway to do this more efficiently?

Thanks,
Peter Brooker
brooker@toka.ireq-ccfm.hydro.qc.ca

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