Hi:

Here's one way to do it, using ggplot2 and base graphics.

# Simulate a data frame with values between 0 and 1 and a corresponding
frequency
df <- data.frame(val = round(runif(100), 2), freq = rpois(100, 10))

# findInterval assigns the values between 0 and 1 to intervals with width
0.1; you need
# to be careful that you get 10 intervals here rather than 11 - if you get
both 0.00 and 1.00
# as rounded values, you will get 11 intervals, since the intervals are open
on the left.
df$interval <- with(df, findInterval(val, seq(0, 1, by = 0.1), rightmost =
TRUE))

# There are several ways to cumulate the frequencies by interval, but since
I want
# to keep things in data frames (for input to ggplot2), I chose ddply() from
the plyr package,
# but tapply(), aggregate() and several functions in other packages would
also work.
library(ggplot2)       # loads the plyr package as well
tab <- ddply(df, 'interval', summarise, cfreq = sum(freq))

# Generate a bar chart in ggplot2
ggplot(tab, aes(x = interval/10 - 0.05, y = cfreq)) +
   geom_bar(stat = 'identity', fill = 'orange', color = 'orange') +
   labs(x = 'value', y = 'frequency')

# Same graph in base graphics, but here I removed the space between bars.
The
# plot is saved to an object so that the x-axis labels can be replaced.
u <- barplot(tab$cfreq, space = 0, col = 'red', ylim = c(0, 130), xlab =
'Value',
                    ylab = 'Frequency')
axis(1, at = u, labels = u/10)
box()

HTH,
Dennis

On Tue, Mar 29, 2011 at 2:05 AM, Karin Lagesen <karin.lagesen@bio.uio.no>wrote:

> Hi!
>
> I have a dataset that looks like this:
>
> 0.0     14
> 0.0     3
> 0.9     12
> 0.73    15
> 0.78    2
> 1.0     15
> 0.3     2
> 0.32    8
>
> ...and so on.
>
> I.e. a value between 0 and 1, and a number
>
> I would like to plot this in a histogram-like manner. I would like to have
> a set of bins, each 0.1 wide, and plot the sum of values in column 2 that
> falls within each bin. I.e, in this case I would like the first bin, 0.0, to
> have the value 17, the second, 0.1, to have the value 0 and so on, until the
> last bin which has the value 15. I am sadly uncertain of both how to sum
> these together, and also on which plot type to use.
>
> Thanks in advance!
>
> Karin
> --
> Karin Lagesen, Ph.D.
> Centre for Ecological and Evolutionary Synthesis (CEES)
> University of Oslo, Dept. of Biology
> P.O. Box 1066 Blindern 0316 Oslo, Norway
> Ph. +47 22844132 Fax. +47 22854001
> Email karin.lagesen@bio.uio.no
> http://folk.uio.no/karinlag
>
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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