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.lage...@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.lage...@bio.uio.no
> http://folk.uio.no/karinlag
>
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