Here's one way in base R:
df <- data.frame(id=c("A","A","B","B"),
first=c("BX",NA,NA,"LF"),
second=c(NA,"TD","BZ",NA),
third=c(NA,NA,"RB","BT"),
fourth=c("LG","QR",NA,NA))
new_df <- data.frame(do.call(rbind, by(df, df$id, function(x) {
sapply(x[,-1], function(y) {
if (all(is.na(y))) return(NA)
if (all(!is.na(y))) return("clash")
return(as.character(y[which(!is.na(y))]))
})
})))
new_df$id <- rownames(new_df)
rownames(new_df) <- NULL
new_df
## first second third fourth id
## 1 BX TD <NA> clash A
## 2 LF BZ clash <NA> B
On Tue, Aug 18, 2015 at 3:06 PM, Jon BR <jonsle...@gmail.com> wrote:
> df <-
> data.frame(id=c("A","A","B","B"),first=c("BX",NA,NA,"LF"),second=c(NA,"TD","BZ",NA),third=c(NA,NA,"RB","BT"),fourth=c("LG","QR",NA,NA))
>> df
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