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Re: Help needed!! [message #70510 is a reply to message #70509]

Fri, 16 April 2010 09:18

bala murugan
Messages: 23
Registered: April 2010

Junior Member

On Apr 16, 10:10 am, pp <pp.pente...@gmail.com> wrote:
> On Apr 16, 12:49 pm, bala murugan <bala2...@gmail.com> wrote:
>
>> I am new to IDL. This is my first program in IDL. Can somebody point
>> out the errors in my code. I have been struggling to get it right.
>
> If you do not say what you want to do, and what the problem is, we are
> unlikely to guess it.
>
>> FUNCTION poissondist,fLambda,N
>> r = RANDOMU(SEED,1)
>> FOR j=1,N,1 DO BEGIN
>> x=poisson(j,fLambda)
>> if (x EQ r) THEN a[i]=j
>> ENDFOR
>> RETURN,a
>> END
>
> a is never defined, which would cause an error when you try to do
> a[i]=j. However, you seem to avoid this occurring with a condition
> that looks like may never happen (x eq r).

My aim is to do the following,

To write an IDL routine that takes as input the mean of a Poisson
distribution (fLambda = a floating point number >= 0.0) and a number
of realizations (N), and generates N samples from the Poisson
distribution with mean fLambda. The output samples should be provided
as a vector (list) of integers (each >= 0). I will also want to plot
a histogram of the samples (IDL probably has a built-in histogramming
routine).

My subroutine/program will look something like this...

piSamples = PoissonDist(fLambda, N)
piSamples = vector of N integer samples returned by the routine
fLambda = mean of the Poisson distribution
N = number of samples to generate

This routine will need to loop n = 1..N Each time through the loop,
it will need to call RANDOMU to get a random number between 0.0 and
1.0. It will then need to call IMSL_POISSONCDF (probably repeatedly)
to determine which integer in the Poisson distribution corresponds to
the random number gotten from RANDOMU. This integer is then placed in
the output vector, etc.

I am not using IMSL_POISSONCDF. Rather I am calculating the poisson
probability myself.

Can you please help me with this?

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[Message index]

		Re: Help needed!! By: R.G.Stockwell on Sat, 17 April 2010 10:07
		Re: Help needed!! By: R.G.Stockwell on Sat, 17 April 2010 10:04
		Re: Help needed!! By: jeanh on Sat, 17 April 2010 07:57
		Re: Help needed!! By: Craig Markwardt on Fri, 16 April 2010 20:59
		Re: Help needed!! By: bala murugan on Fri, 16 April 2010 12:46
		Re: Help needed!! By: bala murugan on Fri, 16 April 2010 12:19
		Re: Help needed!! By: Gray on Fri, 16 April 2010 12:13
		Re: Help needed!! By: bala murugan on Fri, 16 April 2010 12:11
		Re: Help needed!! By: R.G.Stockwell on Fri, 16 April 2010 11:59
		Re: Help needed!! By: bala murugan on Fri, 16 April 2010 11:06
		Re: Help needed!! By: Gray on Fri, 16 April 2010 10:53
		Re: Help needed!! By: R.G.Stockwell on Fri, 16 April 2010 10:48
		Re: Help needed!! By: Gray on Fri, 16 April 2010 10:47
		Re: Help needed!! By: bala murugan on Fri, 16 April 2010 09:40
		Re: Help needed!! By: bala murugan on Fri, 16 April 2010 09:39
		Re: Help needed!! By: penteado on Fri, 16 April 2010 09:33
		Re: Help needed!! By: Craig Markwardt on Fri, 16 April 2010 09:23
		Re: Help needed!! By: bala murugan on Fri, 16 April 2010 09:18
		Re: Help needed!! By: penteado on Fri, 16 April 2010 09:10
		Re: Help needed!! By: bala murugan on Mon, 19 April 2010 10:16

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