Could anyone help me with the following issue.
Using the GSL library in R I define the following code:
#########
library(gsl);
S<-function(n)
{ r<-0:n;
ans<-sum(gsl_sf_choose(n,r)*(-1)^r*2^(2*r)*gamma_inc(6-2*r,2))
ans }
#########>SS(10) yields 34.91868
>SS(40) yields 5.340422
>SS(60) yields 180.3162
Doing the same computations in maple I get
34.918679360927169740821310620770402166885975646756
5.340473872869891061658721253647686930049562214921
2.2269219454888559341895277572725106
respectively. Is this a precision problem?
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The summands can get pretty large: the 2^(2*r) factor will erase a lot of
precision. Is there another way to compute this? Perhaps use the recurrence
relation for the binomial coefficient to get a recurrence relation for your
function?
Reid Huntsinger
-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Francisco Fuentes
Sent: Thursday, May 05, 2005 2:02 PM
To: r-help at stat.math.ethz.ch
Subject: [R] Precision in R
Could anyone help me with the following issue.
Using the GSL library in R I define the following code:
#########
library(gsl);
S<-function(n)
{ r<-0:n;
ans<-sum(gsl_sf_choose(n,r)*(-1)^r*2^(2*r)*gamma_inc(6-2*r,2))
ans }
#########>SS(10) yields 34.91868
>SS(40) yields 5.340422
>SS(60) yields 180.3162
Doing the same computations in maple I get
34.918679360927169740821310620770402166885975646756
5.340473872869891061658721253647686930049562214921
2.2269219454888559341895277572725106
respectively. Is this a precision problem?
---------------------------------
[[alternative HTML version deleted]]
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R-help at stat.math.ethz.ch mailing list
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PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
Did you try format(x,digits=22). 22 digits is the maximum supported. I hope this helps Francisco>From: "Huntsinger, Reid" <reid_huntsinger at merck.com> >To: "'Francisco Fuentes'" <franciscofuentes2005 at yahoo.co.uk>, >r-help at stat.math.ethz.ch >Subject: RE: [R] Precision in R >Date: Thu, 5 May 2005 14:18:50 -0400 > >The summands can get pretty large: the 2^(2*r) factor will erase a lot of >precision. Is there another way to compute this? Perhaps use the recurrence >relation for the binomial coefficient to get a recurrence relation for your >function? > >Reid Huntsinger > >-----Original Message----- >From: r-help-bounces at stat.math.ethz.ch >[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Francisco Fuentes >Sent: Thursday, May 05, 2005 2:02 PM >To: r-help at stat.math.ethz.ch >Subject: [R] Precision in R > > >Could anyone help me with the following issue. >Using the GSL library in R I define the following code: > >######### >library(gsl); >S<-function(n) >{ r<-0:n; >ans<-sum(gsl_sf_choose(n,r)*(-1)^r*2^(2*r)*gamma_inc(6-2*r,2)) >ans } >######### > >SS(10) yields 34.91868 > >SS(40) yields 5.340422 > >SS(60) yields 180.3162 >Doing the same computations in maple I get > >34.918679360927169740821310620770402166885975646756 >5.340473872869891061658721253647686930049562214921 >2.2269219454888559341895277572725106 > >respectively. Is this a precision problem? > > > >--------------------------------- > > [[alternative HTML version deleted]] > >______________________________________________ >R-help at stat.math.ethz.ch mailing list >https://stat.ethz.ch/mailman/listinfo/r-help >PLEASE do read the posting guide! >http://www.R-project.org/posting-guide.html > >______________________________________________ >R-help at stat.math.ethz.ch mailing list >https://stat.ethz.ch/mailman/listinfo/r-help >PLEASE do read the posting guide! >http://www.R-project.org/posting-guide.html