Hi,
On Sat, Sep 3, 2011 at 12:54 AM, Noah Silverman <noahsilver...@ucla.edu> wrote:
> Hi,
>
> Just starting to learn about Rcpp tonight (Using it through the inline
> library)
>
> I'm attempting to construct a matrix and then fill it with values as I
> iterate through my function. The results are wrong. Am I accessing the
> cells of the matrix incorrectly?
You are accessing the cells just fine, but you are using the wrong operator.
"^" is a bitwise OR in C++
You are in need of the `pow` function, ie:
R> library(inline)
R> fx <- cxxfunction(
signature(),
plugin="Rcpp",
body="
Rcpp::NumericMatrix out_xx(10, 4);
for(int i = 1; i != 10; i++){
out_xx(i,0) = i;
out_xx(i,1) = pow(i,2);
out_xx(i,2) = pow(i,3);
out_xx(i,3) = pow(i,4);
}
return Rcpp::wrap(out_xx);
")
R> fx()
[,1] [,2] [,3] [,4]
[1,] 0 0 0 0
[2,] 1 1 1 1
[3,] 2 4 8 16
[4,] 3 9 27 81
[5,] 4 16 64 256
[6,] 5 25 125 625
[7,] 6 36 216 1296
[8,] 7 49 343 2401
[9,] 8 64 512 4096
[10,] 9 81 729 6561
-steve
> The idea was to have an integer in the first position of each row, and then
> the polynomials in the subsequent positions.
>
> Any suggestions?
>
> ----------------------------
>
> Here is my test code:
>
> Test2 <- cxxfunction(
> signature(),
> plugin="Rcpp",
> body="
>
> Rcpp::NumericMatrix out_xx(10, 4);
> for(int i = 1; i != 10; i++){
> out_xx(i,0) = i;
> out_xx(i,1) = i^2;
> out_xx(i,2) = i^3;
> out_xx(i,3) = i^4;
>
> }
> return Rcpp::wrap(out_xx);
>
> "
> )
>
> -----------------------------
>> Test2()
> [,1] [,2] [,3] [,4]
> [1,] 0 0 0 0
> [2,] 1 3 2 5
> [3,] 2 0 1 6
> [4,] 3 1 0 7
> [5,] 4 6 7 0
> [6,] 5 7 6 1
> [7,] 6 4 5 2
> [8,] 7 5 4 3
> [9,] 8 10 11 12
> [10,] 9 11 10 13
>
>
> --
> Noah Silverman
> UCLA Department of Statistics
> 8117 Math Sciences Building #8208
> Los Angeles, CA 90095
>
> _______________________________________________
> Rcpp-devel mailing list
> Rcpp-devel@lists.r-forge.r-project.org
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>
--
Steve Lianoglou
Graduate Student: Computational Systems Biology
| Memorial Sloan-Kettering Cancer Center
| Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact
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