custom graphing of box and whisker plots

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custom graphing of box and whisker plots

briannamwright
Hi,

I'm trying to graph some data in a boxplot-like style, but I want to set
the box and whisker limits myself (rather than having R calculate them for
me). I'd like the boxes to be shaded and the whiskers to be dotted lines.
My data are set up is something like this:

min.whisker    max.whisker     min.box    max.box      species
0                    200                  20            37               A
0                    150                  0              10               B
10                  55                    12             20              B

etc... I have a categorical variable (species) which I'd like to use to
group the boxes along the x-axis of the graph. I tried to do this by
plotting a blank graph and adding the boxes and lines individually using
the lines() function, but it was labour intensive, inelegant, and I
couldn't get the bars in each group (species) not to overlap with one
another.

Does anyone know how to accomplish a graph like this in R with more
succinct coding and/or a custom graphing package? Thanks!

Regards,
Brianna

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Re: custom graphing of box and whisker plots

Mark Difford
On Jun 28, 2012 at 9:08pm Brianna Wright wrote:

> I'm trying to graph some data in a boxplot-like style, but I want to set the box and whisker limits myself...

See ?bxp and ?boxplot for the format of the data you need to pass to bxp. (You just have to add the median to what you have provided in your example.)

Regards, Mark.
Mark Difford (Ph.D.)
Research Associate
Botany Department
Nelson Mandela Metropolitan University
Port Elizabeth, South Africa
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Re: custom graphing of box and whisker plots

briannamwright
Hi Mark,
Thanks for your help - I took a look at ?bxp and ?boxplot. I guess I'm just uncertain about how to specify "z"  in bxp(), not sure I'm quite understanding how the function works.

Thanks,
Brianna
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Re: custom graphing of box and whisker plots

Peter Ehlers
On 2012-06-29 11:09, briannamwright wrote:
> Hi Mark,
> Thanks for your help - I took a look at ?bxp and ?boxplot. I guess I'm just
> uncertain about how to specify "z"  in bxp(), not sure I'm quite
> understanding how the function works.

Just generate the list; see the Value section in ?boxplot.
It seems that all you need is a list consisting of two
components: 'stats', a matrix of the relevant numbers,
and 'names'. Use your data to construct a 5-row, 3-column
matrix. Each column should have, _in the appropriate order_,
the 5 values listed on the help page for boxplot. Your
original post did not specify medians; just make up any
number that falls inside the box and use a transparent
colour for the median line in the plot.

Say you call your matrix M. Then

   z <- list(stats = M, names = c("A", "B", "C"))

can be fed to bxp:

   bxp(z, medcol = 0, whisklty = "dotted", boxfill = "green")

for example.

Peter Ehlers

>
> Thanks,
> Brianna
>
> --
> View this message in context: http://r.789695.n4.nabble.com/custom-graphing-of-box-and-whisker-plots-tp4634826p4634917.html
> Sent from the R help mailing list archive at Nabble.com.

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