Average dataframe data in r by column value

Question

I am trying to automate averaging the data in a data frame that has the same value in a column.

Here the code for simulated data frame

col1 <- c(1,1,1,2,2,2,3,3,3)
col2 <- c(10,20,15,5,8,7,30,1,25)
col3 <- c(.5,.4,.2,.2,.2,.1,.4,.5,.9)
testdf <- data.frame(col1,col2,col3)

And the output from that data frame

testdf
  col1 col2 col3
1    1   10  0.5
2    1   20  0.4
3    1   15  0.2
4    2    5  0.2
5    2    8  0.2
6    2    7  0.1
7    3   30  0.4
8    3    1  0.5
9    3   25  0.9

What I m trying to do is get an output that gives me the averages of the values in columns 2 and 3 for all data with the same value in column 1 (i.e., the average for column 2 values when column 1 values are 1 is 15 and the average for column 3 when column 1 values are 1 is .367)

Does this answer your question? [Calculate the mean by group](https://stackoverflow.com/questions/11562656/calculate-the-mean-by-group) — Andrew, Jan 21 '20 at 17:15
It did answer my question but I had to wait 5 minutes to accept the answer. — ObviousScully, Jan 21 '20 at 17:28
Does this answer your question? [in R, how to calculate mean of all column, by group?](https://stackoverflow.com/questions/40947288/in-r-how-to-calculate-mean-of-all-column-by-group) — camille, Jan 21 '20 at 18:36
Yes, it does answer my question. I did not see that question when I was searching for it before posting though. Sorry. — ObviousScully, Jan 22 '20 at 22:43

akrun · Accepted Answer · 2020-01-21T17:07:19.153

2

We can use aggregate from base R

aggregate(.~ col1, testdf, mean)

Or with dplyr

library(dplyr)
testdf %>%
  group_by(col1) %>%
  summarise_all(mean)

Or with data.table

library(data.table)
setDT(testdf)[, lapply(.SD, mean), by = col1]

edited Jan 21 '20 at 17:07

answered Jan 21 '20 at 17:01

akrun

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Thank you very much. This answers my question. – ObviousScully Jan 21 '20 at 17:28

Average dataframe data in r by column value

1 Answers1