histogram method for S4 class.

On 8/24/05, ernesto <ernesto at ipimar.pt> wrote:
 

Hi,

I'm trying to develop an histogram method for a class called "FLQuant"
which is used by the package FLCore (http://flr-project.org). FLQuant is
an extension to "array". There is an as.data.frame method that coerces
flquant into a data.frame suitable for lattice plotting. The problem is
that when I coerce the object and plot it after it works but if the
method is applied within the histogram method it does not work. See the
code below (the FLCore package is here
http://prdownloads.sourceforge.net/flr/FLCore_1.0-1.tar.gz?download)

   

library(FLCore)
     

Loading required package: lattice
   

data(ple4)
histogram(~data|year, data=ple4 at catch.n)
     

Error in inherits(x, "factor") : Object "x" not found
   

histogram(~data|year, data=as.data.frame(ple4 at catch.n))
     

The catch.n slot is a FLQuant object and the code for histogram is the
following

setMethod("histogram", signature(formula="formula", data="FLQuant"),
   function (formula, data = parent.frame(), allow.multiple =
is.null(groups) || outer,
       outer = FALSE, auto.key = FALSE, aspect = "fill", panel =
"panel.histogram", prepanel = NULL,
       scales = list(), strip = TRUE, groups = NULL, xlab, xlim, ylab,
ylim,
       type = c("percent", "count", "density"),
       nint = if (is.factor(x)) length(levels(x)) else
round(log2(length(x)) + 1),
       endpoints = extend.limits(range(x[!is.na(x)]), prop = 0.04),
       breaks = if (is.factor(x)) seq(0.5, length = length(levels(x)) +
1) else do.breaks(endpoints, nint),
       equal.widths = TRUE, drop.unused.levels =
lattice.getOption("drop.unused.levels"), ...,
       default.scales = list(), subscripts = !is.null(groups), subset =
TRUE) {

       qdf <- as.data.frame(data)

       histogram(formula, data = qdf, allow.multiple = allow.multiple,
outer = outer,
           auto.key = auto.key, aspect = aspect, panel = panel,
prepanel = prepanel, scales = scales,
           strip = strip, groups = groups, xlab=xlab, xlim=xlim,
ylab=ylab, ylim=ylim, type = type,
           nint = nint, endpoints = endpoints, breaks = breaks,
equal.widths = equal.widths,
           drop.unused.levels = drop.unused.levels, ..., default.scales
= default.scales,
           subscripts = subscripts, subset = subset)
   }
)


Any ideas ?
   

[I'm CC-ing to r-devel, please post follow-ups there]

What version of lattice are you using? Please use the latest one, in
which histogram is an S3 generic, with only one argument, formula. The
eventual solution to your problem may involve changing that, but the
first question to ask is whether any other formula makes sense in your
context (if not, I would rather keep one argument and dispatch on
signature(formula = "FLQuant").

Disclaimer: I haven't actually had time to check out FLCore yet, I
will as soon as I can.

Deepayan