R: t test over multiple columns using t.test function

Question

I tried to perform independent t-test for many columns of a dataframe. For example, i created a data frame

set seed(333)
a <- rnorm(20, 10, 1)
b <- rno         


        

Answer 1

As you asked for a for loop:

  a <- rnorm(20, 10, 1)
  b <- rnorm(20, 15, 2)
  c <- rnorm(20, 20, 3)
  grp <- rep(c('m', 'y'),10)
  test_data <- data.frame(a, b, c, grp)  

  meanM=NULL
  meanY=NULL
  p.value=NULL

  for (i in 1:(ncol(test_data)-1)){
    meanM=as.data.frame(rbind(meanM, t.test(test_data[,i] ~ grp)$estimate[1]))
    meanY=as.data.frame(rbind(meanY, t.test(test_data[,i] ~ grp)$estimate[2]))
    p.value=as.data.frame(rbind(p.value, t.test(test_data[,i] ~ grp)$p.value))
   }

  cbind(meanM, meanY, p.value)

It works, but I am a beginner in R. So maybe there is a more efficient solution