alongChrom {geneplotter}R Documentation

A function for plotting expression data from an exprset for a given chromosome.


Given a particular exprset object, a chromLocation object, and a chromosome name, will plot selected exprSet data using various methods.


   alongChrom(eSet, chrom, specChrom,  xlim, whichGenes, 
   plotFormat=c("cumulative", "local","image"),
   xloc=c("equispaced", "physical"), 
   geneSymbols=FALSE, byStrand=FALSE, colors="red", lty=1, type="S",


eSet The exprset object to be used.
chrom The desired chromosome.
specChrom An object of type chromLocation for the species being represented.
xlim A pair of values - either character or integer, which will denote the range of genes to display (based on base pair: either directly in the case of integers, or using the locations of the named genes if character). If not supplied, the entire chromosome is used.
whichGenes If supplied, will limit the displayed genes to the ones provided in this vector.
xloc Determines whether the X axis points (gene names) will be displayed according to their relative position on the chromosome (physical), or spaced evenly (equispaced). Default is equispaced.
plotFormat Determines the method which to plot the data.
scale Determines what method of scaling will be applied to the data. Default is none.
geneSymbols Notes whether to use Affy IDs or Gene Symbols, default is Affy IDs
byStrand Determines whether to show the entire plot at once, or a split plot by strands. Default is a singular plot
lty A vector of line types, which will be cycled.
type Plot type, from par. Defaults to "S".
colors A vector of colors for the plots, which will be cycled.
... Any remaining graphics commands may be passed along as per plot()


The genes on the chromosome of interest are extracted from the chromLocation object passed in, which are then intersected with the genes listed in the exprset. These remaining genes will then be plotted according to the plotFormat argument. If image is specified, an image plot is created showing the expression levels of the samples by gene, using a colour map to denote the levels. If cumulative is chosen, the cumulative expression level is plotted against the genes for each sample. Likewise, if local is used, the raw data is plotted for each sample against the genes using a boxplot format.

Not all parameters are honored for all plotformats. xloc, lty, and type are only used with the cumulative plotformat.


Jeff Gentry


   ## A bit of a hack to not have a package dependency on hgu95av2
   ## but need to fiddle w/ the warn level to not fail the example anyways.
   curWarn <- options(warn=0)
   on.exit(options(warn=curWarn$warn), add=TRUE)
   if (require(hgu95av2)) {
      z <- buildChromLocation("hgu95av2")
      lty <- c(1, 2, 3, 4, 5)
      cols <- c("red", "green", "blue", "orange", "magenta", "black")
      cols <- cols[eset$cov3]
      if (interactive()) {

      ## Here we're using xlim to denote a physical region to display
      xlim <- c(87511280,127717880)
      for (xl in c("equispaced", "physical"))
        for (sc in c("none","rangescale"))
           alongChrom(eset, "1", z, xlim=xlim, xloc=xl,
              plotFormat="cumulative", scale=sc,lty=lty, col=cols)

     ## Here we're looking for specific genes
     which <- c("31540_at","31583_at", "31508_at", "31529_at", "31439_f_at",
     ## Gene "31529_at" does not exist in the current set of genes,
     ## here it demonstrates how genes not available are dropped.
      for (xl in c("equispaced", "physical"))
        for (sc in c("none","rangescale"))
            alongChrom(eset, "1", z, which=which, xloc=xl,
               plotFormat="cumulative", scale=sc,lty=lty, col=cols)

      ## Do an image plot
      for (bs in c(TRUE,FALSE))
         alongChrom(eset, "1",z, xlim=xlim, plotFormat="image",
                   scale="zscale", byStrand=bs)

      ## A boxplot
      for (st in c(TRUE,FALSE))
         alongChrom(eset, "1", z, plotFormat="local",
                    colors=cols, byStrand=st)
    } else print("Example can not be run without the hgu95av2 data package")

[Package geneplotter version 1.8.0 Index]