calculate mean for multiple columns in data.frame

Question

Just wondering whether it is possible to calculate means for multiple columns by just using the mean function

e.g.

mean(iris[,1])

i

Answer 1

With sapply + Filter:

sapply(Filter(is.numeric, iris), mean)
Sepal.Length  Sepal.Width Petal.Length  Petal.Width 
    5.843333     3.057333     3.758000     1.199333 

With dplyr:

library(dplyr)
iris %>% summarise_each(funs(mean))
   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
1:     5.843333    3.057333        3.758    1.199333      NA

PS: in dplyr you can now use summarize_if,

iris %>% summarise_if(is.numeric, mean)
#>   Sepal.Length Sepal.Width Petal.Length Petal.Width
#> 1     5.843333    3.057333        3.758    1.199333

With data.table:

library(data.table)
iris <- data.table(iris)
iris[,lapply(.SD, mean)]
   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
1:     5.843333    3.057333        3.758    1.199333      NA