Hello,
On a more cosmetic level, you could use the pow function from sugar:
require( Rcpp )
require( inline )
fx<- cxxfunction(
signature(),
plugin="Rcpp",
body="
Rcpp::NumericMatrix out_xx(10, 4);
for(int i=0; i<4; i++)
out_xx(_,i) = pow( seq(0, 9), i ) ;
return out_xx;
")
fx()
Apart from the use of the sugar version of pow, also note that you do
not need to wrap out_xx, as this implicit (Rcpp::NumericMatrix converts
itself to a SEXP).
Romain
Le 03/09/11 08:51, Steve Lianoglou a écrit :
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
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--
Romain François
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr
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