[R] stacking histograms

[Rajarshi Guha]

Hi,
  I have a set of observations which are divided into two sets A and B.
I have some code that bins the dataset into 10 bins based on the max and
min of the observed values. 

I would like to make a histogram of A & B using my calculated bins but
plot the distribution of B on top of A (like a stacked barplot). This is
possible since both sets A & B are binned using the same bin ranges.

I have my data in the format:

-4.000000 -3.453000 23
-3.453000 -2.906000 1
-2.906000 -2.359000 5
-2.359000 -1.812000 5
-1.812000 -1.265000 5
-1.265000 -0.718000 13
-0.718000 -0.171000 21
-0.171000 0.376000 49
0.376000 0.923000 26
0.923000 2.017000 13

where the first column is the lower value for the bin, the second column
the upper value for the bin and the last column is the frequency for
that bin

When I call the hist() function I get

> depv <- scan('depv.txt') # a vector of observed values
>
> # the bin boundaries described above
> breakvals <- read.table('bindata.txt') 
>
> hist(depvt, breaks=breakvals$V1)
>
Error in hist.default(depvt, breaks = br$V1) :
        some `x' not counted; maybe `breaks' do not span range of `x'

I get the same error when I specify breakvals$V2. 

Some of my observed values lie beyond the lower boundary of the last bin
(last item of column 1) or below the upper boundary of my first bin
(first row of column 2). Is this the reason why this error occurs?

How should I specify the breaks?

In addition is there any way I can plot the two histograms on top of
each other?

I have tried using the barplot() function but when it comes to marking
the x axis I'm not sure a to how to proceed. What I have been doing is
to calculate the mid point of each bin and use that as the label for
each column - is this a valid way to represent the histogram? (This way
it is easy for me to plot the histograms for the two sets together)

Thanks

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Rajarshi Guha <rxg218 at psu.edu> <http://jijo.cjb.net>
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"A fractal is by definition a set for which the Hausdorff Besicovitch
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