sum columns with similar names in R

Question

I\'ve got a dataframe that\'s got lots of columns that are something like this:

data <- data.frame (a.1 = 1:5, a.2b = 3:7, a.5 = 5:9, bt.16 = 4:8, bt.1234         


        

Answer 1

data <- data.frame (a.1 = 1:5, a.2b = 3:7, a.5 = 5:9, bt.16 = 4:8, bt.12342 = 7:11)
i <- grepl("a.", names(data), fixed = TRUE)
result <- data.frame(a=rowSums(data[, i]), bt=rowSums(data[, !i]))
result
# > result
#    a bt
# 1  9 11
# 2 12 13
# 3 15 15
# 4 18 17
# 5 21 19

If you have more than two prefixes you can do something like:

prefs <- c("a.", "bt.")
as.data.frame(lapply(prefs, function(p) rowSums(data[, grepl(p, names(data), fixed = TRUE)]) ))