Hello,
You should post a data example, like the posting guide says. If your
dataset is large, use something like
dput(head(dat, 20)) # paste the output of this in your post.
where 'dat' is your dataset.
Now, try
# make up some data
set.seed(12)
dat <- matrix(c(sort(rnorm(10)), sample(letters[1:4], 10, TRUE)), ncol=2)
colnames(dat) <- c("A", "col10")
dat
# this does it
ix <- as.logical(ave(seq_len(nrow(dat)), dat[, "col10"],
FUN=function(x) ifelse(x == min(x), TRUE, FALSE)))
dat[ix, ] # rows 1, 2, 4, 6
Hope this helps,
Rui Barradas
Em 07-06-2012 17:07, Seungyeul Yoo escreveu:
Hi all,
I have a matrix with 10000 rows and 10 columns. The last columns contains
another identifiers but the values are not uniques so that I want to generate
another matrix with rows with unique values in the last column.
If I did
tmp<-unique(my_mat$col10)
this will give me 8560 unique entries so the ideal matrix will be 8560X10
columns now then.
I tried
sub_mat<-my_mat[tmp,]
but it generated weird results with many "NA" values and the order was not
changed. The original matrix was ranked from top so I don't want to lose the order too.
For the similar problem, I have used "match" function and do some manipulate to
identify the index of the first appearance of each value but is there any better and neat
way to achieve the same function?
Thanks,
Seungyeul Yoo
Postdoc Fellow,
Institute of Genomics and Multiscale Biology
Department of Genetics and Genomic Sciences
Mount Sinai School of Medicine
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
