Stats on every n rows for each column

Question

I would like to calculate the mean and standard deviation for every nth (in my case every 6) rows (or samples). The following function gives me the means for every 6 rows (96 ro

Answer 1

I think a possible reason that you got Error, warning message is because you applied it directly on the data.frame. For example

set.seed(48)
d1 <- as.data.frame(matrix(sample(1:40, 80*96, replace=T), ncol=80))
rowMeans(matrix(d1, ncol=6, byrow=T))
#Error in rowMeans(matrix(d1, ncol = 6, byrow = T)) : 'x' must be numeric
#In addition: Warning message:
#In matrix(d1, ncol = 6, byrow = T) :
#  data length [80] is not a sub-multiple or multiple of the number of rows [14]

You could unlist the data.frame

 res <- rowMeans(matrix(unlist(d1), ncol=6, byrow=T))
 dim(res) <- c(96/6, 80)
length(res)
#[1] 1280

Crosschecking the results from @Matthew Lundberg's method

res1 <- sapply(d1, function(x) colMeans(matrix(x, nrow=6)))

all.equal(res,res1, check.attributes=F)
[1] TRUE