Gabor Grothendieck <ggrothendieck <at> myway.com> writes:
:
: F Duan <f.duan <at> yale.edu> writes:
:
: > I have a data frame with n columns: X1, X2, ., Xn. Now I want to create a
: > new column: if X1 = X2 = . = Xn, the value is 1; Otherwise, the value is 0.
:
: Here is one possibility if your data frame is all numeric:
:
: x$new <- (sd(t(x))==0)+0
:
: x is the data frame, new is the new column, sd(t(x)) is TRUE for
: rows with zero standard deviation (which occurs iff the entries
: are all zero) and FALSE otherwise and +0 converts that to 1 or 0.
^^^^
"zero" should be replaced by "the same".
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