Replacing values of one matrix from another

[yves.claveau@mnr.gov.on.ca]

Replacing values of one matrix from another

Dear S-Plus users,
        I am presently doing some data handling with S-Plus 6.0 under
Windows NT 4 and I am stuck with a problem. I want to replace values in a
matrix from values in a smaller one. I have:

dataa

tree    dbh     ht      tag
1       12      7       0
2       15      9       0
3       18      12      0
4       10      5       0
5       21      14      0

and

subplot

tree    tag
1       1
4       1

and I want to have

dataa

tree    dbh     ht      tag
1       12      7       1
2       15      9       0
3       18      12      0
4       10      5       1
5       21      14      0

        I thought using:

if (subplot[,1] = dataa[1,]) {dataa[,4] <- 1}

        but S-Plus only uses the first line of each matrix. I then used a
less elegant solution by using the MERGE function with data frames:

datab <- merge(as.data.frame(dataa),as.data.frame(subplot),by="tree",
all.x=T)
datab$tag <- datab$tag.x+datab$tag.y
datac <- data.matrix(datab)
remove.col(datac, "tag.x",1) 
remove.col(datac, "tag.y",1)

        but for some strange reasons I cannot get rid of the columns created
by the merge function.

        I tried an even less elegant approach by using FOR loops and IF but
I cannot get the results I want. What should I do?

        Regards

      Yves Claveau

-------------------------------------------
Yves Claveau, M.Sc. F.
Ontario Forest Research Institute
1235 Queen St. E.
Sault Ste Marie, ON
P6A 2E5

Ph.: (705) 946-2981 ext. 252
Fax.: (705) 946-2030
Email: yves.claveau@mnr.gov.on.ca