[Rcpp-devel] not sure if it's a rcpp question or a cpp question

[Dirk Eddelbuettel]

On 14 March 2013 at 14:42, Aileen Lin wrote:
| My C code:
| //[[Rcpp::depends("Rcpp")]]
| #include <Rcpp.h>
| #include <iostream>
| using namespace Rcpp;
|  
| //[[Rcpp::export]]
| NumericVector sigmutest(double pd, double rsq){
|   double qpd = R::qnorm(pd, 0, 1, 1, 0);
|   double sgtemp = 0.2;
|   double sg = 0.3;
|   double eor = 1;
|  
|   double w = 0;
|   while (eor>=0.0001) { 
|         sg = sgtemp;
|         w = pd * 0.4 / (R::pnorm((qpd - sqrt(rsq) * (-0.42) * sgtemp),
| 0, 1, 1, 0));
|         sgtemp = (-0.5) * w + 0.4;
|         std::cout << "sg " << sg << std::endl;
|         std::cout << "sgtemp " << sgtemp << std::endl;
|         eor = abs(sg - sgtemp);
|        
|         std::cout << "error " << eor << std::endl;
|        
|       }
|   NumericVector out(3);
|   out(0) = sg;
|   out(1) = sgtemp;
|   out(2) = eor;
|   return out; 
| }
| 
| My R code:
| 
| > Rcpp::sourceCpp('src/sbi.cpp')
| > x <- sigmutest(0.0002327279, 0.1025499338)
| sg 0.2
| sgtemp 0.219135
| error 0
| 
|  
| Does anyone know what is going on? Thanks.

abs() is a C function for int-on-int. So eor becomes 0. 

Use std::fabs() instead.

Dirk

| --
| Aileen L.
| 
| View my Linkedin profile: http://au.linkedin.com/in/aileen2
| 
| 
| Being happy doesn't mean you're perfect. It just means you've decided to look
| beyond the imperfections- K.B Indiana (age 14)
| 
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-- 
Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com