计算 R 中多列数据的总和、均值和方差

Question

I'm new to R. The professor asked us to obtain sum, mean and variance for several columns of data which are in Excel form. Now, I want to try to use R to solve them rather than enter the formula in Excel and drag. I have imported the data into R and they are correctly displayed. I can use the commands sum () and sd () and var () for EACH column.

My question is: is there a way to let R display the sum, sd, and variance for each column at the same time? (Rather than calculating these again and again for each column).

I mean something like colSum(col1, col2, col3,...) and the line just shows the sum for each column.

Answer 1

More generally you would do something like:

sapply(data, sum)
sapply(data, var)
sapply(data, sd)

Or in one line as suggested by Agile Bean:

sapply(data, function(x) c(sum=sum(x), var=var(x), sd=sd(x)))

Answer 2

I just figured it out. Basically I need to use colSums() and colMeans(). For example, colSums (,data[2:5]). This means we can calculate the sum for each column from column 2 to column 5.