I received a lot of good advice how to remove NaN columns - thank you all
!!!
The simplest mechanism to center/scale and remove NaN columns seems to be
> xdata <- data.frame(A = 3:1, B = 1:3, rep(9, 3))
> xs <- scale(xdata)
> mask <- sapply(as.data.frame(xs), function(x) all(is.nan(x)))
> scaled.centered.x <- as.data.frame(xs)[!mask]
> scaled.centered.x
A B
1 1 -1
2 0 0
3 -1 1
Note that as.data.frame(xs) is important, because apparently xs from
scale() function
is not a data frame and if as.data.frame() is omitted in the code fragment
above we get something like this
> mask <- sapply(xs, function(x) all(is.nan(x)))
> xs[!mask]
1 2 3 <NA> <NA> <NA>
1 0 -1 -1 0 1
Maybe somebody more knowledgeable could give some explanation for this
behavior.
Ryszard
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