Because a histogram is descriptive and makes no assumptions about what it
describes? Attaching a probability to the bars assumes that some random
draw is being made. Suppose my data is a count of computers running a
particular OS. What would be the value in reporting this as a probability
that a randomly chosen computer is running Ubuntu? Density is more
universal, IMO.
--------------------------------------
Jonathan P. Daily
Technician - USGS Leetown Science Center
11649 Leetown Road
Kearneysville WV, 25430
(304) 724-4480
"Is the room still a room when its empty? Does the room,
the thing itself have purpose? Or do we, what's the word... imbue it."
- Jubal Early, Firefly
r-help-boun...@r-project.org wrote on 01/13/2011 01:37:01 PM:
> [image removed]
>
> [R] Question about histogram
>
> Longe
>
> to:
>
> r-help
>
> 01/13/2011 03:11 PM
>
> Sent by:
>
> r-help-boun...@r-project.org
>
> Dear list,
>
> 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?
>
> Regards,
> L.
>
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