[R] subsetting of factor
a.ramasamy at imperial.ac.uk
Fri Sep 12 17:26:33 CEST 2008
help(rowttests) says that fac needs to be a factor. So how about ?
m <- matrix( rnorm(30), nc=6 )
genotype <- c("a", "a", "b", "b", "c", "c")
w1 <- which( genotype %in% c("a", "b") )
w2 <- which( genotype %in% c("a", "c") )
w3 <- which( genotype %in% c("b", "c") )
list( ab = rowttests( m[ , w1], factor( genotype[w1] ) ),
ac = rowttests( m[ , w2], factor( genotype[w2] ) ),
bc = rowttests( m[ , w3], factor( genotype[w3] ) ) )
Hui-Yi Chu wrote:
> Dear R list,
> I think my question maybe easy for you but I really spent entire day to
> resolve it.
> Say I have a matrix, rows are 6000 genes, columns(1-6) are 3 genotypes
> (a,b,c) with 2 repeat.
> I have to use two groups each time for t-test, a vs. c or b vs. c, but I
> dont know how to write correct codes.
> Below is my codes, the last two lines are needed to be corrected....
> ef <- exprs(esetsub)
> kk <- factor(esetsub$genotype == c("a", "c"))
> tt <- rowttests(ef[,c(1,2,5,6)], kk)
> ps. column 1-6 is a,a,b,b,c,c
> depending on the document, the kk should be a factor..
> Any suggestions are really appreciated!!
> Best regards,
> [[alternative HTML version deleted]]
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