x<- 1:10; y<- 1:15; z<- outer( x,y,"+")
image.plot(x,y,z)
# or obj<- list( x=x,y=y,z=z); image.plot(obj)
# now add some points on diagonal with some clipping anticipated
points( 5:12, 5:12, pch="X", cex=3)
image.plot(x,y,z, legend.lab="inches")
# adding breaks and distinct colors for intervals of z
# with and without lab.breaks
brk<- quantile( c(z))
image.plot(x,y,z, breaks=brk, col=rainbow(4))
# annotate legend strip just at break values
image.plot(x,y,z, breaks=brk, col=rainbow(4),
lab.breaks=names(brk))
#
# compare to
quantile(c(z), c( .05, .1,.5, .9,.95))-> zp
image.plot(x,y,z,
axis.args=list( at=zp, labels=names(zp) ) )
# a log scaling for the colors
ticks<- c( 1, 2,4,8,16,32)
image.plot(x,y,log(z), axis.args=list( at=log(ticks), labels=ticks))
# see help file for designer.colors to generate a color scale that adapts to
# quantiles of z.
#
#fat (5 characters wide) and short (50\% of figure) color bar on the bottom
image.plot( x,y,z,legend.width=5, legend.shrink=.5, horizontal=TRUE)
# adding label with all kinds of additional arguments.
# use side=4 for vertical legend and side= 1 for horizontal legend
# to be parallel to axes. See help(mtext).
image.plot(x,y,z,
legend.args=list( text="unknown units",
col="magenta", cex=1.5, side=4, line=2))
#### example using a irregular quadrilateral grid
data( RCMexample)
image.plot( RCMexample$x, RCMexample$y, RCMexample$z[,,1])
#### multiple images with a common legend
set.panel()
# Here is quick but quirky way to add a common legend to several plots.
# The idea is leave some room in the margin and then over plot in this margin
par(oma=c( 0,0,0,4)) # margin of 4 spaces width at right hand side
set.panel( 2,2) # 2X2 matrix of plots
# now draw all your plots using usual image command
for ( k in 1:4){
image( matrix( rnorm(150), 10,15), zlim=c(-4,4), col=tim.colors())
}
par(oma=c( 0,0,0,1))# reset margin to be much smaller.
image.plot( legend.only=TRUE, zlim=c(-4,4))
# image.plot tricked into plotting in margin of old setting
set.panel() # reset plotting device
#
# Here is a more learned strategy to add a common legend to a panel of
# plots consult the split.screen help file for more explanations.
# For this example we draw two
# images top and bottom and add a single legend color bar on the right side
# first divide screen into the figure region and legend colorbar on the
# right to put a legend.
split.screen( rbind(c(0, .8,0,1), c(.8,1,0,1)))
# now divide up the figure region
split.screen(c(2,1), screen=1)-> ind
zr<- range( 2,35)
# first image
screen( ind[1])
image( x,y,z, col=tim.colors(), zlim=zr)
# second image
screen( ind[2])
image( x,y,z+10, col=tim.colors(), zlim =zr)
# move to skinny region on right and draw the legend strip
screen( 2)
image.plot( zlim=zr,legend.only=TRUE, smallplot=c(.1,.2, .3,.7),
col=tim.colors())
close.screen( all=TRUE)
# you can always add a legend arbitrarily to any plot;
# note that here the plot is too big for the vertical strip but the
# horizontal fits nicely.
plot( 1:10, 1:10)
image.plot( zlim=c(0,25), legend.only=TRUE)
image.plot( zlim=c(0,25), legend.only=TRUE, horizontal =TRUE)
# combining the usual image function and adding a legend
# first change margin for some more room
par( mar=c(10,5,5,5))
image( x,y,z, col=topo.colors(64))
image.plot( zlim=c(0,25), nlevel=64,legend.only=TRUE, horizontal=TRUE,
col=topo.colors(64))
#
#
# sorting out the difference in formatting between matrix storage
# and the image plot depiction
A<- matrix( 1:48, ncol=6)
# Note that matrix(c(A), ncol=6) == A
image.plot(1:8, 1:6, A)
# add labels to each box
text( c( row(A)), c( col(A)), A)
# and the indices ...
text( c( row(A)), c( col(A))-.25,
paste( "(", c(row(A)), ",",c(col(A)),")", sep=""), col="grey")
# "columns" of A are horizontal and rows are ordered from bottom to top!
#
# matrix in its usual tabular form where the rows are y and columns are x
image.plot( t( A[6:1,]), axes=FALSE)Run the code above in your browser using DataLab