[R] join columns

[David Winsemius]

On Aug 10, 2011, at 11:04 AM, Anthony Ching Ho Ng wrote:

> Dear R-help,
>
> I wonder if you could give me some suggestions in how to do a union
> join of two data frames as follow:
> -> union join the common column, and insert a 0 if one is missing.
>
> I made a function to perform the following, and I know it may not that
> quite welly written, but it works.
>
> Any suggestions are welcome, many thanks.
>
> Anthony
>
>> q1 = data.frame(a=1,b=2,c=3,row.names="q1")
>     a b c
> q1 1 2 3
>
>> q2 = data.frame(d=4,b=1,a=4, row.names="q2")
>     d b a
> q2 4 1 4
>
> ->  myJoinColumns(q1,q2)
>     a b c d
> q1 1 2 3 0
> q2 4 1 0 4

 > temp <- merge(q1,q2, all=TRUE)
 > temp[is.na(temp)] <- 0
 > temp
   a b c d
1 1 2 3 0
2 4 1 0 4
>
>
> myJoinColumns <- function(q1,q2){
>  allNames = sort(union(colnames(q1),colnames(q2)))
>  for (i in 1:length(allNames)){
>    t1 = which(colnames(q1) == allNames[i])
>    t2 = which(colnames(q2) == allNames[i])
>
>    if (length(t1) == 1){
>      sec1 = q1[,t1]
>    } else {
>      sec1 = 0
>    }
>
>    if (length(t2) == 1){
>      sec2 = q2[,t2]
>    } else {
>      sec2 = 0
>    }
>
>    if (i == 1){
>      qTable = matrix(c(sec1,sec2))
>    }else{
>      qTable = cbind(qTable,c(sec1,sec2))
>    }
>  }
>  colnames(qTable) = allNames
>  rownames(qTable) = c("q1","q2")
>  qTable
> }
>
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David Winsemius, MD
West Hartford, CT