[Rd] rmultinom.c error probability not sum to 1
Dear all,
I have a questions regarding using the c function rmultinom.c.
I got the following error message "rbinom: probability sum should be 1, but is
0.999264"
Which is thrown by:
if(fabs((double)(p_tot - 1.)) > 1e-7)
MATHLIB_ERROR(_("rbinom: probability sum should be 1, but is %g"),
(double) p_tot);
I understand my probabilities do not sum to one close enough. I tried the
following,
p[2] = 1. - p[0] - p[1], where 'p', are the probabilities but this is not
sufficient to pass the error message!
Thanks in advance!
Regards,
Maarten
(I don't think this is an issue with versions but I used R version 3.2.3 and
can provide more details on my linux build if necessary.)
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Re: [Rd] rmultinom.c error probability not sum to 1
Hi all,
I should have given a better explanation of my problem. Here it is.
I extracted from my code the bit that gives the error. Place this in a file
called test.c
#include
#include
#include
#include
#include
int main(){
double prob[3] = {0.0, 0.0, 0.0};
double prob_tot = 0.;
prob[0] = 0.3*dnorm(2, 0, 1, 0);
prob[1] = 0.5*dnorm(5, 0, 1, 0);
prob[2] = 0.2*dnorm(-3, 0, 1, 0);
//obtain prob_tot
prob_tot = 0.;
for(int j = 0; j < 3; j++)
prob_tot += prob[j];
//normalize probabilities
for(int j = 0; j < 3; j++)
prob[j] = prob[j]/prob_tot;
//or this give the same error
//prob[2] = 1.0 - prob[1] - prob[0];
//checking indeed prob_tot not exactly 1
for(int j = 0; j < 3; j++)
prob_tot += prob[j];
Rprintf("Prob_tot: %f\n", prob_tot);
int rN[3];
rmultinom(1, prob, 1, rN);
return 0;
}
run R CMD SHLIB test.c to generate the test.so. Now from within R
> dyn.load("test.so")
> .C("main")
Prob_tot: 1.017084
Error: rbinom: probability sum should be 1, but is 0.948075
Maybe I miss some trivial C knowledge why this is not exactly one!
Thanks in advance!
Regards,
Maarten
From: peter dalgaard [pda...@gmail.com]
Sent: Thursday, March 10, 2016 1:26 PM
To: Iterson, M. van (MOLEPI)
Cc: r-devel@r-project.org
Subject: Re: [Rd] rmultinom.c error probability not sum to 1
On 10 Mar 2016, at 12:47 , m.van_iter...@lumc.nl wrote:
> Dear all,
>
> I have a questions regarding using the c function rmultinom.c.
>
> I got the following error message "rbinom: probability sum should be 1, but
> is 0.999264"
>
> Which is thrown by:
>
> if(fabs((double)(p_tot - 1.)) > 1e-7)
> MATHLIB_ERROR(_("rbinom: probability sum should be 1, but is %g"),
> (double) p_tot);
>
> I understand my probabilities do not sum to one close enough. I tried the
> following,
> p[2] = 1. - p[0] - p[1], where 'p', are the probabilities but this is not
> sufficient to pass the error message!
>
p[0]
> Thanks in advance!
>
> Regards,
> Maarten
>
> (I don't think this is an issue with versions but I used R version 3.2.3 and
> can provide more details on my linux build if necessary.)
>
>
>
> [[alternative HTML version deleted]]
>
> __
> R-devel@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd@cbs.dk Priv: pda...@gmail.com
__
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] rmultinom.c error probability not sum to 1
Thanks for your replies. Indeed, I had to add the dimension of the probability
vector like this
rmultinom(1, prob, 3, rN);
Regards,
Maarten
From: peter dalgaard [pda...@gmail.com]
Sent: Thursday, March 10, 2016 9:45 PM
To: Iterson, M. van (MOLEPI)
Cc: r-devel@r-project.org
Subject: Re: [Rd] rmultinom.c error probability not sum to 1
> On 10 Mar 2016, at 21:25 , m.van_iter...@lumc.nl wrote:
>
> Hi all,
>
> I should have given a better explanation of my problem. Here it is.
>
> I extracted from my code the bit that gives the error. Place this in a file
> called test.c
Aha. Missing info #1, C not R...
>
> #include
> #include
> #include
> #include
> #include
>
> int main(){
>
> double prob[3] = {0.0, 0.0, 0.0};
> double prob_tot = 0.;
>
> prob[0] = 0.3*dnorm(2, 0, 1, 0);
> prob[1] = 0.5*dnorm(5, 0, 1, 0);
> prob[2] = 0.2*dnorm(-3, 0, 1, 0);
>
> //obtain prob_tot
> prob_tot = 0.;
> for(int j = 0; j < 3; j++)
>prob_tot += prob[j];
>
> //normalize probabilities
> for(int j = 0; j < 3; j++)
>prob[j] = prob[j]/prob_tot;
>
> //or this give the same error
> //prob[2] = 1.0 - prob[1] - prob[0];
>
prob_tot = 0; missing here
> //checking indeed prob_tot not exactly 1
> for(int j = 0; j < 3; j++)
>prob_tot += prob[j];
>
> Rprintf("Prob_tot: %f\n", prob_tot);
>
> int rN[3];
> rmultinom(1, prob, 1, rN);
Er, where do you tell rmultinom that variates are three-dimensional? It's not
going to infer it from array sizes.
-pd
> return 0;
> }
>
> run R CMD SHLIB test.c to generate the test.so. Now from within R
>
>> dyn.load("test.so")
>> .C("main")
> Prob_tot: 1.017084
> Error: rbinom: probability sum should be 1, but is 0.948075
>
> Maybe I miss some trivial C knowledge why this is not exactly one!
>
> Thanks in advance!
>
> Regards,
> Maarten
>
> From: peter dalgaard [pda...@gmail.com]
> Sent: Thursday, March 10, 2016 1:26 PM
> To: Iterson, M. van (MOLEPI)
> Cc: r-devel@r-project.org
> Subject: Re: [Rd] rmultinom.c error probability not sum to 1
>
> On 10 Mar 2016, at 12:47 , m.van_iter...@lumc.nl wrote:
>
>> Dear all,
>>
>> I have a questions regarding using the c function rmultinom.c.
>>
>> I got the following error message "rbinom: probability sum should be 1, but
>> is 0.999264"
>>
>> Which is thrown by:
>>
>> if(fabs((double)(p_tot - 1.)) > 1e-7)
>> MATHLIB_ERROR(_("rbinom: probability sum should be 1, but is %g"),
>> (double) p_tot);
>>
>> I understand my probabilities do not sum to one close enough. I tried the
>> following,
>> p[2] = 1. - p[0] - p[1], where 'p', are the probabilities but this is not
>> sufficient to pass the error message!
>>
>
>
> p[0]
>
>
>> Thanks in advance!
>>
>> Regards,
>> Maarten
>>
>> (I don't think this is an issue with versions but I used R version 3.2.3 and
>> can provide more details on my linux build if necessary.)
>>
>>
>>
>> [[alternative HTML version deleted]]
>>
>> __
>> R-devel@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>
> --
> Peter Dalgaard, Professor,
> Center for Statistics, Copenhagen Business School
> Solbjerg Plads 3, 2000 Frederiksberg, Denmark
> Phone: (+45)38153501
> Office: A 4.23
> Email: pd@cbs.dk Priv: pda...@gmail.com
>
--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd@cbs.dk Priv: pda...@gmail.com
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R-devel@r-project.org mailing list
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