[R] mosaic.by(): vectorizing args passed by apply()?

[John Fox]

Dear Mike,

There might be a  more elegant solution, but one way is slice the table 
into a list of tables corresponding to the panels of the display, and to 
use a for loop to index panels and titles:

     mosaic.by <-
     function(table, by=NULL, ...)
     {
         n <- length(dim(table))
         if(n == 0)
             stop("invalid table `table'")
         if(length(by)>1)
             stop("Sorry, cannot handle >1 by variable yet.")

         np <- dim(table)[by]
         name <- names(dimnames(table))[by]
         titles <- paste(name, ":", dimnames(table)[[by]])

         opar <- par( mfrow=c(np, np), usr=c(1,1000,1,1000), mar=rep(1,4)) 
# why np x np?
         on.exit(par(opar))
         panels <- apply(table, by, list)
         for (i in 1:np) mosaicplot(panels[[i]][[1]], main=titles[i], 
shade=T, ...)
     }

Does that do what you want?

Regards,
  John

At 04:56 PM 11/30/2001 -0500, Michael Friendly wrote:
>I've just started learning R, so I'm still on the steep part of the
>learning curve, but my enthusiasm was heightened by learning that
>there's a very nice implementation of mosaicplot().
>
>As a learning project, I've already done a basic implementation
>of a pairs.table() function which does a mosaic scatterplot matrix,
>and now I'm trying to do conditional mosaic plots (discrete analog
>of a coplot).
>
>I found that
>    apply(table, by, mosaicplot,...)
>worked quite nicely, but I want to label each mosaic with the
>combination of the factor name and level value, e.g., Sex: Male,
>and I can't figure out how to get just one element of a list
>passed by apply as an argument.
>
>In the function below, titles is a list like:
> > paste("Sex: ", dimnames(Titanic)[[2]])
>[1] "Sex:  Male"   "Sex:  Female"
>and I want each element passed as the main= value for the corresponding
>slice of the table.
>Can someone help?
>
>Try the function below with
>
>data(HairEyeColor)
>mosaic.by(HairEyeColor, 3)
>
>## Conditional mosaics, one for each level of the by-variable(s)
>##   -- how to add factor levels as main= ?
>##   -- how to do for more than one by-variable?
>mosaic.by <-
>function(table, by=NULL, ...)
>{
>     n <- length(dim(table))
>     if(n == 0)
>         stop("invalid table `table'")
>     if(length(by)>1)
>         stop("Sorry, cannot handle >1 by variable yet.")
>
>     np <- dim(table)[by]
>     name <- names(dimnames(table))[by]
>     titles <- paste(name, ":", dimnames(table)[[by]])
>
>     opar <- par( mfrow=c(np, np), usr=c(1,1000,1,1000), mar=rep(1/2,4))
>     on.exit(par(opar))
>
>     apply(table, by, mosaicplot, main=titles, shade=T, legend=F, ...)
>}
>
>thx,
>-Michael
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-----------------------------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada L8S 4M4
email: jfox at mcmaster.ca
phone: 905-525-9140x23604
web: www.socsci.mcmaster.ca/jfox
-----------------------------------------------------

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