explanation-of-apply.R

set.seed(1)
x1 <- rnorm(10)
x2 <- rnorm(10)
out <- cbind(x1, x2)
colMeans(out)

# colMeans can be computed as follows as well
apply(out, 2, mean)

# apply - applies a mean function to column (indicated by 2) of out matrix

# for sd change mean to sd
apply(out, 2, sd)

# this is equivalent to 
c(sd(out[, 1]), sd(out[, 2]))

# for median
apply(out, 2, median)

# this is equivalent to 
c(median(out[, 1]), median(out[, 2]))