| defining functions on-the-fly [message #25130] |
Tue, 22 May 2001 15:30  |
mperrin+news
Messages: 81
Registered: May 2001
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Member |
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I would like to be able to define some functions on-the-fly in IDL.
In other words, my program does some stuff, and computes that the desired
function is (some arbitrary function, not necessarily a polynomial).
I would then like to define the equivalent of
FUNCTION myfunction, x,y
return, <my arbitrary expression in (x,y)>
END
and then be able to call myfunction(x,y).
Is there any easier way to do this than actually writing out a
myfunction.pro file to disk and compiling that? That way would certainly
work, but it strikes me as inelegant... At first I thought I could do this
with the EXECUTE statement, but you can't define functions using that.
- Marshall
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| Re: defining functions on-the-fly [message #25206 is a reply to message #25130] |
Wed, 23 May 2001 15:01  |
dirk
Messages: 15
Registered: March 1998
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Junior Member |
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In article <9eh94p$3ce$1@agate.berkeley.edu>,
Marshall Perrin <mperrin+news@arkham.berkeley.edu> wrote:
> Marc Schellens <m_schellens@hotmail.com> wrote:
>> try .comp:
>>
>> IDL> .comp [ENTER]
>> - function f
>> - return,42
>> - end
>> % Compiled module: F.
>> IDL> print,f()
>> 42
>> IDL>
>
> No, this doesn't work for what I have in mind - .comp is an executive command
> and so can only be used interactively. You can't use .comp in a procedure. I
> want *my software* to be able to define functions on the fly, not myself. So
> it looks like the best solution really is writing out a new .PRO file to the
> disk and compiling that.
I faced the same problem a while back, and this writing out solution was
unacceptable as well. The problem for me was that subsequent iterations
of the program would write a different equation in the .PRO file, but IDL
has already compiled a function by that name and doesn't look at or
recompile the new .PRO file. Since .comp and .run are executive level,
you can't force it to either.
This is what I did: (I had to interactively have N gaussians in a
fitting program)
;prepare expressions for fitting and result plotting
plotresult = 'model=convol(exp((-1.)*(0.0'
FOR i=0, ncomp-1 DO $
plotresult = plotresult + ' + Gauss1(v,result['+strtrim(string(3*i), 2)+ $
':'+strtrim(string(2+3*i), 2)+'])'
plotresult = plotresult+')), normspreadfunc, /center, /edge_truncate)'
; then
done = execute(plotresult)
; and you can do
oplot, v, model, color=200, thick=3
I wasn't clear on why execute wasn't working for you... Perhaps this
helps.
Cheers, Dirk
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