[R] How to detect if a vector is FP constant?

Hadley Wickham hadley at rice.edu
Tue Nov 9 01:45:00 CET 2010

Hi all,

What's the equivalent to length(unique(x)) == 1 if want to ignore
small floating point differences?  Should I look at diff(range(x)) or
sd(x) or something else?  What cut off should I use?

If it helps to be explicit, I'm interested in detecting when a vector
is constant for the purpose of visual display.  In other words, if I
rescale x to [0, 1] do I have enough precision to get at least 100
unique values.



Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University

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