r - Mean per group in a data.frame -

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• aggregate / summarize multiple variables per group (i.e. sum, mean, etc) 4 answers

i have data.frame , need calculate mean per group (i.e. per month, below).

name     month  rate1     rate2 aira       1      12        23 aira       2      18        73 aira       3      19        45 ben        1      53        19 ben        2      22        87 ben        3      19        45 cat        1      22        87 cat        2      67        43 cat        3      45        32 

my desired output below, values rate1 , rate2 group means. please disregard value, have made example.

name       rate1       rate2 aira        23.21       12.2 ben         45.23       43.9 cat         33.22       32.2 

this type of operation aggregate designed for:

d <- read.table(text='name     month  rate1     rate2 aira       1      12        23 aira       2      18        73 aira       3      19        45 ben        1      53        19 ben        2      22        87 ben        3      19        45 cat        1      22        87 cat        2      67        43 cat        3      45        32', header=true)  aggregate(d[, 3:4], list(d$name), mean)    group.1    rate1    rate2 1    aira 16.33333 47.00000 2     ben 31.33333 50.33333 3     cat 44.66667 54.00000 

here aggregate columns 3 , 4 of data.frame d, grouping d$name, , applying mean function.

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or, using formula interface:

aggregate(. ~ name, d[-2], mean)