Question

The data set that I’m working with is similar to the one below (although the example is of a much smaller scale, the data I’m working with is 10’s of thousands of rows) and I haven’t been able to figure out how to get R to add up column data based on the group number. Essentially I want to be able to get the number of green(s), blue(s), and red(s) added up for all of group 81 and 66 separately and then be able to use that information to calculate percentages.

txt <- "Group Green Blue Red Total
81 15 10 21 46
81 10 10 10 30
81 4 8 0 12
81 42 2 2 46
66 11 9 1 21
66 5 14 5 24 
66 7 5 2 14
66 1 16 3 20
66 22 4 2 28"

dat <- read.table(textConnection(txt), sep = " ", header = TRUE)

I’ve spent a good deal of time trying to figure out how to use some of the functions on my own hoping I would stumble across a proper way to do it, but since I’m such a new basic user I feel like I have hit a wall that I cannot progress past without help.

Answer 1

One way is via aggregate. Assuming your data is in an object x:

aggregate(. ~ Group, data=x, FUN=sum)
#   Group Green Blue Red Total
# 1    66    46   48  13   107
# 2    81    71   30  33   134