Display a rectangle filled with an arbitrary color gradient

gradient.rect draws a rectangle consisting of nslices subrectangles of the colors in col or those returned by color.gradient if col is NULL. The rectangle is 'sliced' in the direction specified by gradient.

Usage

gradient.rect(xleft,ybottom,xright,ytop,reds,greens,blues,col=NULL,
  nslices=50,gradient="x",border=par("fg"))

Arguments

xleft,ybottom,xright,ytop: Positions of the relevant corners of the desired rectangle, as in rect.
reds,greens,blues: vectors of the values of the color components either as 0 to 1 or ,if any value is greater than 1, 0 to 255.
col: Vector of colors. If supplied, this takes precedence over reds, greens, blues and nslices will be set to its length.
nslices: The number of sub-rectangles that will be drawn.
gradient: whether the gradient should be horizontal (x) or vertical.
border: The color of the border around the rectangle (NA for none).

Value

the vector of hexadecimal color values from color.gradient or

col.

Author

Jim Lemon

Examples

 # get an empty box
 plot(0:10,type="n",axes=FALSE)
 # run across the three primaries
 gradient.rect(1,0,3,6,reds=c(1,0),
  greens=c(seq(0,1,length=10),seq(1,0,length=10)),
  blues=c(0,1),gradient="y")
 # now a "danger gradient"
 gradient.rect(4,0,6,6,c(seq(0,1,length=10),rep(1,10)),
  c(rep(1,10),seq(1,0,length=10)),c(0,0),gradient="y")
 # now just a smooth gradient across the bar
 gradient.rect(7,0,9,6,col=smoothColors("red",38,"blue"),border=NA)