Append occurrence counter to entries in a character vector

appendCounter.R

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## appendCounter Function ##
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## Author: Thomas Girke
## Last update: 04-Oct-15

## Function to append occurrence counter to entries in character 
## vector and return the results as named vector where the 
## original data are in the same order in the data slot
## and the counting result in the name slot.
appendCounter <- function(x, sep="_") {
    names(x) <- sprintf(paste0("%0", as.character(nchar(length(x))+1), "d"), seq_along(x))
    tmp <- sort(x)
    f <- table(tmp)
    tmp2 <- unlist(sapply(names(f), function(z) paste(z, 1:f[z], sep=sep)))
    names(tmp2) <- names(tmp)
    names(x) <- tmp2[sort(names(tmp2))]
    return(x)
}
## Usage:
# x <-  c("a", "b", "c", "b", "h", "c")                                            
# appendCounter(x, sep="_")