data(giaever)
## Find the 3000 most variable genes, according to sd/mean:
varMeas <- function(vec, na.rm=TRUE)
{
if(na.rm)
vec <- vec[!is.na(vec)]
if(length(vec) == 0)
measure <- NA
else
measure <- sd(vec)/mean(vec)
return(measure)
}
variability <- apply(giaever, 1, varMeas)
rks <- rank(variability)
giaever3000 <- giaever[rks>length(rownames(giaever))-3000,]
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