DATA MINING
Desktop Survival Guide by Graham Williams |
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Remove Variables with no Variance |
We also only want columns where there is some variance in the values, so also remove those columns with a minimum value equal to the maximum. Again, use is made of lapply to apply a function (in this case max and min) to the data.
> rmcols <- as.numeric(lapply(dat, min, na.rm=T)) == as.numeric(lapply(dat, max, na.rm=T)) > rmcols <- rev(seq(1,ncol(dat))[rmcols]) > for (i in rmcols) dat[[i]] <- NULL > ncol(dat) [1] 59 |