### specplot.R: Use the rpanel package to interactively plot spectra.
### $Id: specplot.R,v 1.2 2007/07/30 09:14:39 bhm Exp $

### Copyright © 2007 Bjørn-Helge Mevik
### This program is free software; you can redistribute it and/or modify
### it under the terms of the GNU General Public License version 2 as
### published by the Free Software Foundation.
###
### This program is distributed in the hope that it will be useful,
### but WITHOUT ANY WARRANTY; without even the implied warranty of
### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
### GNU General Public License for more details.

### A copy of the GPL text is available here:
### http://www.gnu.org/licenses/gpl-2.0.txt

### Contact info:
### Bjørn-Helge Mevik
### bhx6@mevik.net
### Rødtvetvien 20
### N-0955 Oslo
### Norway

specplot <- function() {
    ## Make sure the package is loaded
    if (!require(rpanel)) stop("Could not load required package 'rpanel'")
    ## Start a new device, if needed:
    if(dev.cur() == 1) get(getOption("device"))()
    ## Save the device number:
    device <- dev.cur()
    ## Build a call to matplot()
    plotcall <- match.call()
    plotcall[[1]] <- as.name("matplot")
    if (missing(type)) plotcall$type <- "l"
    plotcall$reverse <- plotcall$plot.add <- NULL
    ## Protect plot.add from extra evaluations:
    plot.add <- substitute(plot.add)
    ## Set up range
    if (missing(y) || is.null(y)) ## No good: rx <- xy.coords(x)$x
	x <- 1:NROW(x)
    rx <- range(x)
    p <- length(x)
    minwidth <- 2 * diff(rx) / (p - 1)
    if (missing(reverse)) reverse <- x[1] > x[p]
    ## The callback function:
    replot <- function(panel) {
        ## Add a modified xlim argument to the matplot call:
        halfwidth <- max(panel$width, minwidth) / 2 # rpanel isn't perfect!
        if (reverse)
	      xlim <- 2*mean(rx) - panel$center + c(halfwidth, -halfwidth)
        else
            xlim <- panel$center + c(-halfwidth, halfwidth)
        plotcall$xlim <- xlim
        ## Save the current device:
        dev.save <- dev.cur()
        ## Switch to the original device:
        dev.set(device)
        ## Do the plot
        eval(plotcall)
        ## Do any addons:
        eval(plot.add)
        ## Switch back to the current device:
        dev.set(dev.save)
        ## Return the panel
        panel
    }
    panel <- rp.control("specplot", center = mean(rx), width = diff(rx))
    rp.slider(panel, center, min(x), max(x), replot)
    rp.slider(panel, width, minwidth, diff(rx), replot)
}
## Create and add a list of formals:
fm <- formals(matplot)                  # Use matplot's formals as a start
fm$type <- "l"                          # Change default
fm$xlim <- NULL                         # Remove argument
fm <- c(fm, list(reverse = FALSE, plot.add = NULL)) # Add arguments
formals(specplot) <- fm