On Wed, Apr 25, 2012 at 02:22:05PM +0200, Patrick Hausmann wrote:
> Hello,
>
> I am trying to get a new vector 'x1' based on the not NA-values in
> column 'a' and 'b'. I found a way but I am sure this is not the best
> solution. So any ideas on how to "optimize" this would be great!
>
> m <- factor(c("a1", "a1", "a2", "b1", "b2", "b3", "d1", "d1"), ordered
> = TRUE)
> df <- data.frame( a= m, b = m)
> df[1,1] <- NA
> df[4,2] <- NA
> df[2,2] <- NA
> df[6,1] <- NA
> df
>
> w <- !apply(df, 2, is.na)
> v <- apply(w, 1, FUN=function(L) which(L == TRUE)[[1]])
>
> for (i in 1:nrow(df) ) {
> g[i] <- df[i, v[i]]
> }
>
> df$x1 <- g
Hello.
The above code does not initialize g. Adding the command
g <- rep(NA, times=nrow(df))
i get the same as using
df$x1 <- ifelse(is.na(df$a), df$b, df$a)
df
a b x1
1 <NA> a1 1
2 a1 <NA> 1
3 a2 a2 2
4 b1 <NA> 3
5 b2 b2 4
6 <NA> b3 5
7 d1 d1 6
8 d1 d1 6
The codes are obtained, since the original data frame contains
factors. If the intention is to keep character values, then use
df$x1 <- ifelse(is.na(df$a), as.character(df$b), as.character(df$a))
df
a b x1
1 <NA> a1 a1
2 a1 <NA> a1
3 a2 a2 a2
4 b1 <NA> b1
5 b2 b2 b2
6 <NA> b3 b3
7 d1 d1 d1
8 d1 d1 d1
Hope this helps.
Petr Savicky.
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