[R] create new column to combine 2 data.frames

[Mat]

Thanks first.

that doesn't look bad. But if have a equal ID in dat2, the days are no
longer correct.

the correct data.frame has to look like this one:

  ID Name Management Training
1  1 Jack          1        3
2  2 John          1        0
3  3 Jill          0        4

not this one:

  ID Name Management Training
1  1 Jack          1        1
2  2 John          3        0
3  3 Jill          0        1

> dat1 <- read.table(text = "
+ ID Name
+ 1  Jack
+ 2  John
+ 3  Jill
+ ", header = TRUE, stringsAsFactors = FALSE)
> 
> dat2 <- read.table(text = "
+ ID  Days  Type
+ 1    1       Management 
+ 1    3       Training
+ 2    1       Management
+ 3    4       Training
+ ", header = TRUE, stringsAsFactors = FALSE)
> 
> library(reshape2)
> tmp <- dcast(data = dat2, ID ~ Type, value.var = "Type")
> 
> tmp[-1] <- lapply(tmp[-1], function(x){
+ y <- integer(length(x))
+ y[!is.na(x)] <- dat2[["Days"]][!is.na(x)]
+ y})
> result <- merge(dat1, tmp)
> result
  ID Name Management Training
1  1 Jack          1        1
2  2 John          3        0
3  3 Jill          0        1
> 



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