[R] merge, cbind, or....?

[Sundar Dorai-Raj]

Bruno Cutayar wrote:
> 
> 
> Hi,
> i have two data.frame x and y like :
>  > x <- data.frame( num = c(1:10), value = runif(10) )
>  > y <- data.frame( num = c(6:10), value = runif(5) )
> and i want to obtain something like :
> 
> num.x    value.x     num.y   value.y
>      1 0.38423828    NA 0.2911089
>      2 0.17402507    NA 0.8455208
>      3 0.54443465    NA 0.8782199
>      4 0.04540406    NA 0.3202252
>      5 0.46052426    NA 0.7560559
>      6 0.61385464     6 0.2911089
>      7 0.48274968     7 0.8455208
>      8 0.11961778     8 0.8782199
>      9 0.64531394     9 0.3202252
>    10 0.92052805    10 0.7560559
> 
> with NA in case of missing value for y to x.
> 
> { for this example : i write simply
>  > data.frame(num.x=c(1:10), 
> value.x=x[[2]],num.y=c(rep(NA,5),6:10),value.y=y[[2]]) }
> 
> I didn't find solution in merge(x,y,by="num") : missing rows are no 
> keeping.
> Can't you help me ?
> 

See ?merge which will tell you about the `all' argument. I believe you 
want something like (though I'm not completely sure):

m <- merge(x, y, by = "num", all = TRUE)
# now add `num.x' and `num.y' as in your example
na.x <- is.na(m$value.x)
na.y <- is.na(m$value.y)
m$num.x <- ifelse(m$num %in% x$num, m$num, NA)
m$num.y <- ifelse(m$num %in% y$num, m$num, NA)
# fill in `value.x' and `value.y' with repeated values
m$value.x[na.x] <- rep(x$value, length.out = sum(na.x))
m$value.y[na.y] <- rep(y$value, length.out = sum(na.y))

HTH,

--sundar