[R] Question about histogram
longeliver at gmail.com
Thu Jan 13 19:37:01 CET 2011
I'm new to R, please bear with my silly questions. I'm trying to get an
understanding of why the results I get from a call to hist() are not as
I thought I would get. When I use the parameter freq=FALSE, I think the
plot will contain bars that none of them is larger than 1, because
they're probabilities. But for my code, the bars exceeded 1.
The actual data seems immaterial. I tried with dummy data:
> hist(runif(1000), freq=FALSE)
and the histogram includes bars well over 1 in height. The man page
says that freq=FALSE produces densities, so that the total area is 1.
Clearly if all the values are between 0 and 1, as is the case here, some
of the bars stand out above 1, for the area to be 1. I thought that it
is the sum of the bar heights that would be 1, so that the bars reflect
probabilities for each interval, rather than densities. So, the answer
to my question would be "because it's densities, not probabilities", but
then the question is, why densities and not probabilities?
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