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Re: I need a bit of help....Convol and functions [message #50532 is a reply to message #50455]

Wed, 04 October 2006 06:43

James Kuyper
Messages: 425
Registered: March 2000

Senior Member

D.Kochman@gmail.com wrote:
>> Yes, func() needs to create an array for CONVOL() to convolve. However,
>> sumex should already be an array, in order for this code to work as
>> intended, and this code does nothing to change any aspect of sumex. I'm
>> not sure I understand what you mean by the comment "but its a
>> function".
>
>
> Thanks for the help, slowly but surely I'm starting to get it. What I
> meant by "but its a function" is I just don't see how sumex is an
> array. If I were to put
>
> sumex = X
>
> that to me makes sumex a function, namely, f(x)=x

No, in IDL, the statement sumex=x would make the variable named sumex
refer to an object which is an exact copy of x. If X is an array, then
sumex will be an array of the same type and shape. In the actual code
you gave us,

sumex=P(0)*exp( -X / P(1) )+P(2)*exp( -X / P(3) )+P(7)*exp( -X / P(8) )

dividing X by P(1) creates a new array with the same shape as X.
Passing that array to exp() produces a result with the same shape as X,
and multiplying it by P(0) also produces an array in the same shape.
The same applies to each of the terms in that sum, and adding all three
terms together also produces an array of the same shape.

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[Message index]

		I need a bit of help....Convol and functions By: D.Kochman@gmail.com on Sun, 01 October 2006 03:42
		Re: I need a bit of help....Convol and functions By: D.Kochman@gmail.com on Wed, 04 October 2006 06:53
		Re: I need a bit of help....Convol and functions By: James Kuyper on Wed, 04 October 2006 06:43

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