[R] Possible to "import" histograms in R?

[(Ted Harding)]

On 15-Aug-07 08:30:08, Nick Chorley wrote:
> Hi,
> 
> I have a large amount of data that I would like to create a
> histogram of and plot and do things with in R. It is pretty
> much impossible to read the data into R, so I have written a
> program to bin the data and now have a list of counts in each
> bin. Is it possible to somehow import this into R and use
> hist(), so I can, for instance, plot the probability density?
> I have looked at the help page for hist(), but couldn't find
> anything related to this there.
> 
> Regards,
> 
> Nicky Chorley

Presumably you now have (or can readily generate) files on your
system whose contents are (or are equivalent to) something like:

brkpts.dat
0.0
0.5
1.0
....
9.5
10.0

counts.dat
10
7
38
....
7
0

where there is one more line in brkpts.dat than in counts.dat

Now simply read both files into R, creating variables 'brkpts',
'counts'

Now create a histogram template (any silly old data will do):

H1 <- hist(c(1,2))

Next, attach your variables to it:

H1$breaks <- brkpts
H1$counts <- counts

and you have your histogram in R. Also, you can use the data
in the variables 'brkpts', 'counts' to feed into any other
procedure which can acept data in this form.

Example (simulating the above in R):

  brkpts<-0.5*(0:20)
  counts<-rpois(20,7.5)
  H1<-hist(c(1,2))
  H1$breaks <- brkpts
  H1$counts <- counts
  plot(H1)

Or, if you want a more "realistic-looking" one, follow on with:

midpts<-(brkpts[1:20]+brkpts[2:21])/2
counts<-rpois(20,100*dnorm(midpts,mean=5,sd=3))
H1$breaks <- brkpts
H1$counts <- counts
plot(H1)


In other words, you've already done R's work for it with your
program which bins the data. All you need to do in R is to get
these results into the right place in R.

Hoping this helps,
Ted.

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E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 15-Aug-07                                       Time: 10:38:05
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