Methods for image() in Package 'Matrix'

image-methods {Matrix}

R Documentation

Methods for image() in Package 'Matrix'

Description

Methods for function image in package Matrix. An image of a matrix simply color codes all matrix entries and draws the n x m matrix using an n x m grid of (colored) rectangles.

The Matrix package image methods are based on levelplot() from package lattice; hence these methods return an “object” of class "trellis", producing a graphic when (auto-) print()ed.

Usage

## S4 method for signature 'dgTMatrix'
image(x,
      xlim = c(1, di[2]),
      ylim = c(di[1], 1), aspect = "iso",
      sub = sprintf("Dimensions: %d x %d", di[1], di[2]),
      xlab = "Column", ylab = "Row", cuts = 15,
      useRaster = FALSE,
      useAbs = NULL, colorkey = !useAbs,
      col.regions = NULL,
      lwd = NULL, border.col = NULL, ...)

Arguments

`x`	a Matrix object, i.e., fulfilling `is(x, "Matrix")`.
`xlim, ylim`	x- and y-axis limits; may be used to “zoom into” matrix. Note that x,y “feel reversed”: `ylim` is for the rows (= 1st index) and `xlim` for the columns (= 2nd index). For convenience, when the limits are integer valued, they are both extended by `0.5`; also, `ylim` is always used decreasingly.
`aspect`	aspect ratio specified as number (y/x) or string; see `levelplot`.
`sub, xlab, ylab`	axis annotation with sensible defaults; see `plot.default`.
`cuts`	number of levels the range of matrix values would be divided into.
`useRaster`	logical indicating if raster graphics should be used (instead of the tradition rectangle vector drawing). If true, `panel.levelplot.raster` (from lattice package) is used, and the colorkey is also done via rasters, see also `levelplot` and possibly `grid.raster`. Note that using raster graphics may often be faster, but can be slower, depending on the matrix dimensions and the graphics device (dimensions).
`useAbs`	logical indicating if `abs(x)` should be shown; if `TRUE`, the former (implicit) default, the default `col.regions` will be `grey` colors (and no `colorkey` drawn). The default is `FALSE` unless the matrix has no negative entries.
`colorkey`	logical indicating if a color key aka ‘legend’ should be produced. Default is to draw one, unless `useAbs` is true. You can also specify a `list`, see `levelplot`, such as`list(raster=TRUE)` in the case of rastering.
`col.regions`	vector of gradually varying colors; see `levelplot`.
`lwd`	(only used when `useRaster` is false:) non-negative number or `NULL` (default), specifying the line-width of the rectangles of each non-zero matrix entry (drawn by `grid.rect`). The default depends on the matrix dimension and the device size.
`border.col`	color for the border of each rectangle. `NA` means no border is drawn. When `NULL` as by default, `border.col <- if(lwd < .01) NA else NULL` is used. Consider using an opaque color instead of `NULL` which corresponds to `grid::get.gpar("col")`.
`...`	further arguments passed to methods and `levelplot`, notably `at` for specifying (possibly non equidistant) cut values for dividing the matrix values (superseding `cuts` above).

Value

as all lattice graphics functions, image(<Matrix>) returns a "trellis" object, effectively the result of levelplot().

Methods

All methods currently end up calling the method for the dgTMatrix class. Use showMethods(image) to list them all.

Examples

showMethods(image)
## If you want to see all the methods' implementations:
showMethods(image, incl=TRUE, inherit=FALSE)

data(CAex)
image(CAex, main = "image(CAex)")
image(CAex, useAbs=TRUE, main = "image(CAex, useAbs=TRUE)")

cCA <- Cholesky(crossprod(CAex), Imult = .01)
## See  ?print.trellis --- place two image() plots side by side:
print(image(cCA, main="Cholesky(crossprod(CAex), Imult = .01)"),
      split=c(x=1,y=1,nx=2, ny=1), more=TRUE)
print(image(cCA, useAbs=TRUE),
      split=c(x=2,y=1,nx=2,ny=1))

data(USCounties)
image(USCounties)# huge
image(sign(USCounties))## just the pattern
    # how the result looks, may depend heavily on
    # the device, screen resolution, antialiasing etc
    # e.g. x11(type="Xlib") may show very differently than cairo-based

## Drawing borders around each rectangle;
    # again, viewing depends very much on the device:
image(USCounties[1:400,1:200], lwd=.1)
## Using (xlim,ylim) has advantage : matrix dimension and (col/row) indices:
image(USCounties, c(1,200), c(1,400), lwd=.1)
image(USCounties, c(1,300), c(1,200), lwd=.5 )
image(USCounties, c(1,300), c(1,200), lwd=.01)
## These 3 are all equivalent :
(I1 <- image(USCounties, c(1,100), c(1,100), useAbs=FALSE))
 I2 <- image(USCounties, c(1,100), c(1,100), useAbs=FALSE,        border.col=NA)
 I3 <- image(USCounties, c(1,100), c(1,100), useAbs=FALSE, lwd=2, border.col=NA)
stopifnot(all.equal(I1, I2), all.equal(I2, I3))
## using an opaque border color
image(USCounties, c(1,100), c(1,100), useAbs=FALSE, lwd=3, border.col = adjustcolor("skyblue", 1/2))

if(doExtras <- interactive() || nzchar(Sys.getenv("R_MATRIX_CHECK_EXTRA")) ||
    identical("true", unname(Sys.getenv("R_PKG_CHECKING_doExtras")))) {
## Using raster graphics: For PDF this would give a 77 MB file,
## however, for such a large matrix, this is typically considerably
## *slower* (than vector graphics rectangles) in most cases :
if(doPNG <- !dev.interactive())
   png("image-USCounties-raster.png", width=3200, height=3200)
image(USCounties, useRaster = TRUE) # should not suffer from anti-aliasing
if(doPNG)
   dev.off()
   ## and now look at the *.png image in a viewer you can easily zoom in and out
}#only if(doExtras)

[Package Matrix version 1.2-17 Index]