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_oplante@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
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
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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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