Is there such "colsd" in R?

Question

I am using in my code colSums but I also need the standard deviation beside the sum. I searched in the internet and found this page which contain only:

colSums colMeans 

http://stat.ethz.ch/R-manual/R-devel/library/base/html/colSums.html

I tried this:

colSd 

but I got this error:

Error: could not find function "colSd" 

How I can do the same thing but for standard deviation:

colSd 

Here is the code:

results <- colSums(x,na.rm=TRUE)#### here I want colsd 

Answer 1

I want to provide a fourth (very similar to @Thomas) approach and some benchmarking:

library("microbenchmark") library("matrixStats")  colSdApply <- function(x, ...)apply(X=x, MARGIN=2, FUN=sd, ...) colSdMatrixStats <- colSds  colSdColMeans <- function(x, na.rm=TRUE) {   if (na.rm) {     n <- colSums(!is.na(x)) # thanks @flodel   } else {     n <- nrow(x)   }   colVar <- colMeans(x*x, na.rm=na.rm) - (colMeans(x, na.rm=na.rm))^2   return(sqrt(colVar * n/(n-1))) }  colSdThomas <- function(x)sqrt(rowMeans((t(x)-colMeans(x))^2)*((dim(x)[1])/(dim(x)[1]-1)))  m <- matrix(runif(1e7), nrow=1e3)  microbenchmark(colSdApply(m), colSdMatrixStats(m), colSdColMeans(m), colSdThomas(m))  # Unit: milliseconds #                 expr      min       lq   median       uq      max neval #        colSdApply(m) 435.7346 448.8673 456.6176 476.8373 512.9783   100 #  colSdMatrixStats(m) 344.6416 357.5439 383.8736 389.0258 465.5715   100 #     colSdColMeans(m) 124.2028 128.9016 132.9446 137.6254 172.6407   100 #       colSdThomas(m) 231.5567 240.3824 245.4072 274.6611 307.3806   100   all.equal(colSdApply(m), colSdMatrixStats(m)) # [1] TRUE all.equal(colSdApply(m), colSdColMeans(m)) # [1] TRUE all.equal(colSdApply(m), colSdThomas(m)) # [1] TRUE 

Answer 2

colSds and rowSds are two of many similar functions in the matrixStats package