Question

Here is small example:

X1 <- c("AC", "AC", "AC", "CA", "TA", "AT", "CC", "CC")
X2 <- c("AC", "AC", "AC", "CA", "AT", "CA", "AC", "TC")
X3 <- c("AC", "AC", "AC", "AC", "AA", "AT", "CC", "CA")
mydf1 <- data.frame(X1, X2, X3)

Input data frame

  X1 X2 X3
1 AC AC AC
2 AC AC AC
3 AC AC AC
4 CA CA AC
5 TA AT AA
6 AT CA AT
7 CC AC CC
8 CC TC CA

The function

# Function 
atgc <- function(x) {
 xlate <- c( "AA" = 11, "AC" = 12, "AG" = 13, "AT" = 14,
"CA"= 12, "CC" = 22, "CG"= 23,"CT"= 24,
 "GA" = 13, "GC" = 23, "GG"= 33,"GT"= 34,
 "TA"= 14,  "TC" = 24, "TG"= 34,"TT"=44,
"ID"= 56, "DI"= 56, "DD"= 55, "II"= 66
 )
  x =   xlate[x]
 }
outdataframe <- sapply (mydf1, atgc)
outdataframe
   X1 X2 X3
AA 11 11 12
AA 11 11 12
AA 11 11 12
AG 13 13 12
CA 12 12 11
AC 12 13 13
AT 14 11 12
AT 14 14 14

Problem, AC is not eaqual to 12 in output rather 11, similarly for others. Just mess !

( Exta: Also I do not know how to get rid of the rownames.)

Answer 1

Just use apply and transpose:

t(apply (mydf1, 1, atgc))

To use sapply, then either use:

1. stringsAsFactors=FALSE when creating your data frame, i.e.

   mydf1 <- data.frame(X1, X2, X3, stringsAsFactors=FALSE)
   

   (thanks @joran) or

2. Change the last line of your function to: x = xlate[as.vector(x)]