On Thu, May 31, 2012 at 8:27 AM, Johannes Radinger <jradin...@gmx.at> wrote:
> Hi,
>
> I have a dataframe and want to remove columns from it
> that are populated with a similar value (for the total
> column) (the variation of that column is 0). Is there an
> easier way than to calculate the statistics and then
> remove them by hand?
>
> A <- runif(100)
> B <- rep(1,100)
> C <- rep(2.42,100)
> D <- runif(100)
> df <- data.frame(A,B,C,D) # if want to conditionally remove column B and C as
> they show no variations
You could try something like:
for (i in seq(ncol(df), 1))
if (length(unique(df[, i])) == 1) {
df[, i] <- NULL
}
or for just numeric values:
for (i in seq(ncol(df), 1))
if (all(mean(df[, i]) == df[, i])) {
df[, i] <- NULL
}
HTH,
James
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