r - Calculate means for multiple variables in with different sizes -

i have table , code @ below:

data <- data.frame(subject = c(0,0,0,1,2,2),                    class = c("apple","apple","apple","orange","orange","orange"),                    name = c(1,1,1,0,1,1),                    name1 = c(0,1,1,1,1,1),                    name2 = c(1,1,1,0,0,1)) 

i want find average of each variable each class , each subject, , list table. example, table have average subject first; 0 mean 8/9 , 2 mean 5/6. second work out mean class; orange mean 2/3. breakdown average name,name1 , name2.

i have tried code below, first store header list , sort subject , class lapply. isnt working.

cols = c(head(data)) data[,lapply(.sd[,cols,with=false],mean),by=class|subject] 

library(reshape2) library(dplyr)  data2 <- melt(data, c("subject", "class"))  data.frame(summarize(group_by(data2, subject, class),                       avg_val = mean(value))) -> table_for_you