cxxfunction 行列を引数とする関数の例

行列を引数とする関数の例

> library(inline)
> src <- '
+ Rcpp::NumericMatrix xcpp(x);
+ int nrows = xcpp.nrow();
+ int ncolumns = xcpp.ncol();
+ for (int i = 0; i < nrows; i++) {
+     for (int j = 0; j < ncolumns; j++) {
+         xcpp[nrows * j + i] *= 2;
+     }
+ }
+ return xcpp;
+ '
> doublematrix <- cxxfunction(signature(x = "numeric"), body = src, plugin="Rcpp")
> print(doublematrix(matrix(1:10, nrow = 2)))
     [,1] [,2] [,3] [,4] [,5]
[1,]    2    6   10   14   18
[2,]    4    8   12   16   20

> src1 <- '
+     Rcpp::NumericMatrix xbem(xbe);
+     int nrows = xbem.nrow();
+     Rcpp::NumericVector gv(g);
+     for (int i = 1; i < nrows; i++) {
+         xbem(i,_) = xbem(i-1,_) * gv[0] + xbem(i,_);
+     }
+     return xbem;
+ '
> funCPP1 <- cxxfunction(signature(xbe = "numeric", g="numeric"), body = src1, plugin="Rcpp")
> A <- matrix(1:12, 3, 4)
> funCPP1(A, 0.5)
     [,1] [,2]  [,3] [,4]
[1,] 1.00  4.0  7.00   10
[2,] 2.50  7.0 11.50   16
[3,] 4.25  9.5 14.75   20

> src <- '
+     Rcpp::NumericMatrix input(x);
+     int nc = input.ncol();
+     Rcpp::NumericMatrix output = clone<NumericMatrix>(input);
+     for (int i = 1; i < nc; i++) {
+         output.column(i) = output.column(i-1)+input.column(i);
+     }
+     return output;
+ '
> row.cumsum <- cxxfunction(signature(x="numeric"), src, plugin="Rcpp")
> (a <- matrix(1:12, 3, 4))
     [,1] [,2] [,3] [,4]
[1,]    1    4    7   10
[2,]    2    5    8   11
[3,]    3    6    9   12
> row.cumsum(a)
     [,1] [,2] [,3] [,4]
[1,]    1    5   12   22
[2,]    2    7   15   26
[3,]    3    9   18   30