Remove specific rows in a matrix/data.frame

try this:
x <- read.table(textConnection("Letter Number
+ a 1
+ a 1
+ b 1
+ b 0
+ c 0
+ c 1
+ d 0
+ d 0"), as.is = TRUE, header = TRUE)
closeAllConnections()
# following assumes that there are pairs of numbers
result <- do.call(rbind, lapply(split(x, x$Letter), function(.pair){
+     if (all(.pair$Number[1L] == .pair$Number)) return(.pair[1L, ])
+     is1 <- which(.pair$Number == 1)
+     if (length(is1) == 1) return(.pair[is1, ])
+     else return(NULL)
+ }))
result
Letter Number
a      a      1
b      b      1
c      c      1
d      d      0

Hi,

imagine the following matrix/data.frame

Letter Number
a 1
a 1
b 1
b 0
c 0
c 1
d 0
d 0

If the numbers for two identical letters are also identical then I want to
remove either the first or the
second row of that letter. If for a letter the numbers are 1 and 0 I want to
remove the row with the 0.

That means if the code works I would and up with the following
matrix/data.frame

Letter Number
a 1
b 1
c 1
d 1

Many thanks,
Syrvn

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What is the problem that you are trying to solve?

Remove specific rows in a matrix/data.frame

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