[Rcpp-devel] Easy way to subset a matrix

Noah Silverman noahsilverman at ucla.edu
Wed Sep 21 06:16:20 CEST 2011


I want to calculate the variance of a subset of a matrix column.

For example, if I wanted the variance of items 3-10 in column 5.

In R, this would be:

x <- matrix(rnorm(100), nrow=10, ncol=10)
varx <- var(x[3:10,5])

In Rcpp, I can construct a matrix object Rcpp::NumericMatrix x
The var function is available thanks to the great Sugar implementation

But, how can I easily reference a subset of a column to calculate the variance?


Noah Silverman
UCLA Department of Statistics
8117 Math Sciences Building #8208
Los Angeles, CA 90095

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