Subtraction based on two factors

Question

My dataframe looks like so:

group <- c(\"A\", \"A\", \"A\", \"A\", \"B\", \"B\", \"B\", \"B\", \"C\", \"C\", \"C\", \"C\", \"C\", \"C\")
value <- c(3:6, 1:         


        

Answer 1

Its not clear why the sample answer in the post has two identical rows in each output group and not just one but at any rate this produces similar output to that shown:

DF <- df[!duplicated(df[-2]), ]
f <- function(x) setNames(
            data.frame(group = x$group[1:2], as.list(- combn(x$value, 2, diff))),
                   c("group", combn(x$type, 2, paste, collapse = "_"))
            )

by(DF, DF$group, f)

giving:

DF$group: A
  group d_e
1     A  -2
2     A  -2
------------------------------------------------------------ 
DF$group: B
  group d_e
1     B  -2
2     B  -2
------------------------------------------------------------ 
DF$group: C
  group d_e d_f e_f
1     C  -2  -4  -2
2     C  -2  -4  -2

REVISED minor improvements.