[R] bwplot: using a numeric variable to position boxplots

[Richard M. Heiberger]

Michael,

I normally do this with the panel.bwplot.intermediate.hh in the HH package.
This function works by plotting each box with its own call to the
underlying panel.bwplot function.

This example from ?HH::position uses the "positioned" class to
determine where to
place the box.

> library(HH)
> ?position
starting httpd help server ... done
> ## boxplots coded by week
> tmp <- data.frame(Y=rnorm(40, rep(c(20,25,15,22), 10), 5),
+                   week=ordered(rep(1:4, 10)))
> position(tmp$week) <- c(1, 2, 4, 8)
>
>        bwplot(Y ~ week, horizontal=FALSE,
+               scales=list(x=list(limits=c(0,9),
+                           at=position(tmp$week),
+                           labels=position(tmp$week))),
+               data=tmp, panel=panel.bwplot.intermediate.hh)
>


Rich

On 5/3/12, Michael Friendly <friendly at yorku.ca> wrote:
> [Env: R 2.14.2 / Win Xp]
>
> In the examples below, I'm using lattice::bwplot to plot boxplots of 4
> variables, grouped by a factor 'epoch'
> which also corresponds to a numeric year.  I'd like to modify the plots
> to position the boxplots according to
> the numeric value of year, but I can't figure out how to do this.
>
> Also, I'd to modify the strip labels that give the variable names to use
> longer variable labels I define below as
> vlab.
>
>  > install.packages("heplots", repos="http://R-Forge.R-project.org")
>  > # requires heplots 0.9-12 for Skulls data
>  > library(heplots)
>  > data(Skulls)
>  >
>  > # make shorter labels for epochs
>  > Skulls$epoch <- factor(Skulls$epoch,
> labels=sub("c","",levels(Skulls$epoch)))
>  > # create year variable
>  > Skulls$year <- rep(c(-4000, -3300, -1850, -200, 150), each=30)
>  > str(Skulls)
> 'data.frame':   150 obs. of  6 variables:
>   $ epoch: Ord.factor w/ 5 levels "4000BC"<"3300BC"<..: 1 1 1 1 1 1 1 1
> 1 1 ...
>   $ mb   : num  131 125 131 119 136 138 139 125 131 134 ...
>   $ bh   : num  138 131 132 132 143 137 130 136 134 134 ...
>   $ bl   : num  89 92 99 96 100 89 108 93 102 99 ...
>   $ nh   : num  49 48 50 44 54 56 48 48 51 51 ...
>   $ year : num  -4000 -4000 -4000 -4000 -4000 -4000 -4000 -4000 -4000
> -4000 ...
>  > table(Skulls$epoch)
>
> 4000BC 3300BC 1850BC  200BC  AD150
>      30     30     30     30     30
>
> This is what I've tried.  I reshape the data to a long format and can
> plot value ~ epoch or value ~ as.factor(year),
> but I really want to space the boxplots according to the  numeric value
> of year.
>
> # better variable labels -- how to incorporate these in the strip labels?
> vlab <- c("maxBreadth", "basibHeight", "basialLength", "nasalHeight")
>
> library(lattice)
> library(reshape2)
> Skulls$year <- rep(c(-4000, -3300, -1850, -200, 150), each=30)
> sklong <- melt(Skulls, id=c("epoch", "year"))
>
> bwplot(value ~ epoch | variable, data=sklong, scales="free",
>      ylab="Variable value",
>      xlab="Epoch",
>      panel = function(x,y, ...) {
>          panel.bwplot(x, y, ...)
>          panel.linejoin(x,y, col="red", ...)
>      }
>      )
>
> bwplot(value ~ as.factor(year) | variable, data=sklong, scales="free",
>      ylab="Variable value",
>      xlab="Year",
>      panel = function(x,y, ...) {
>          panel.bwplot(x, y, ...)
>          panel.linejoin(x,y, col="red", ...)
>      }
>      )
>
>
>
> --
> Michael Friendly     Email: friendly AT yorku DOT ca
> Professor, Psychology Dept.
> York University      Voice: 416 736-5115 x66249 Fax: 416 736-5814
> 4700 Keele Street    Web:   http://www.datavis.ca
> Toronto, ONT  M3J 1P3 CANADA
>
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