Hi:
You can probably do what you want in either ggplot2 or lattice, but I would
recommend at least a couple different approaches:
(1) Plot individual bar charts by combinations of year and period.
This is easy to do in both ggplot2 and lattice: in ggplot2, one
would use geom_bar(x) + facet_grid(year ~ period), where
x is the count variable. The same thing in lattice would be
barchart( ~ x | year * period, data = mydata). Suitable options
can be added to either plot for better presentation. All the plots
are on the same horizontal and vertical scales so that visual
comparisons across the rows and columns are easy to make.
(2) Use a Cleveland dot chart. This is much less wasteful of ink
than bar charts, and multiple groups can be compared without
too much difficulty. See dotplot() in lattice for details. The
VADeaths example is likely the best one to emulate for your
problem. Both the input data structure and plot code matter.
(3) If your purpose is to compare the two groups with respect
to a count variable, a third option is to consider a mosaic plot,
which can be thought of as a 'visual chi-square test'. These
can be found in package vcd, which contains a nice 40+
page vignette to show you in detail how to create a suitable
mosaic plot (and how to interpret it).
I prefer to see R used to promote good graphics and sound statistical
principles. In that spirit, performing a two-factor comparison with count
data is easier, and quite possibly more instructive, with a 2D visual
metaphor (which all three of the suggestions above have in common) than with
the 1D metaphor of multiple dodged/side-by-side bar charts. Of course, this
may be against the standard practice in your field, in which case you have a
decision to make.
HTH,
Dennis
On Wed, Aug 25, 2010 at 6:16 AM, Jordan Ouellette-Plante
jordan_opla...@hotmail.com wrote:
Dear R community,
I am a beginner using the sciplot package to graph barplots. I would like
to be able to graph two x factors (Sampling.year and Period).
Sampling.year: 2006, 2007, 2008, 2009
Period: First, Second, Total
The parameter group is the different species I looked at. They can be
seen in the legend.
The parameter response is the Average percentage cover category of these
species.
I would like the graph so you see on the x axis the years (in a bigger
font) and the period (in smaller font). It would look a bit like the barplot
that can be seen at
http://onertipaday.blogspot.com/2007/05/make-many-barplot-into-one-plot.html,
but with the advantage of the sciplot package.
Thanks a lot for your help!
Jordan
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