r - Rcpp sugar for NumericMatrix -

for numericvector, can subset smaller numericvector using integervector contains positions subset.

e.g. suppose x<-c(1,2,2,3,4,5), idx<-c(1,3,4), , xsub<-x[idx] 1 2 3.

within rcpp, can use xsub=x[idx].

is there similar way subset rows of numericmatrix using integervector?

for example, following code xmatsub=xmat(idx,_) didn't work me.

there isn't way. have manually, not complicated.

numericmatrix res( idx.size(), m.rows() )  ; for( int i=0; i<idx.size(); i++){     res.row(i) = m.row(idx[i]-1) ;  }