Convert between the 5 different coordinate sytems on a graphical device
Takes a set of coordinates in any of the 5 coordinate systems (usr, plt, fig, dev, or tdev) and returns the same points in all 5 coordinate systems.
cnvrt.coords(x, y = NULL, input = c("usr", "plt", "fig", "dev","tdev"))x |
Vector, Matrix, or list of x coordinates (or x and y coordinates), NA's allowed. |
y |
y coordinates (if |
input |
Character scalar indicating the coordinate system of the input points. |
Every plot has 5 coordinate systems:
usr (User): the coordinate system of the data, this is shown by the tick marks and axis labels.
plt (Plot): Plot area, coordinates range from 0 to 1 with 0 corresponding to the x and y axes and 1 corresponding to the top and right of the plot area. Margins of the plot correspond to plot coordinates less than 0 or greater than 1.
fig (Figure): Figure area, coordinates range from 0 to 1 with 0 corresponding to the bottom and left edges of the figure (including margins, label areas) and 1 corresponds to the top and right edges. fig and dev coordinates will be identical if there is only 1 figure area on the device (layout, mfrow, or mfcol has not been used).
dev (Device): Device area, coordinates range from 0 to 1 with 0 corresponding to the bottom and left of the device region within the outer margins and 1 is the top and right of the region withing the outer margins. If the outer margins are all set to 0 then tdev and dev should be identical.
tdev (Total Device): Total Device area, coordinates range from 0 to 1 with 0 corresponding to the bottom and left edges of the device (piece of paper, window on screen) and 1 corresponds to the top and right edges.
A list with 5 components, each component is a list with vectors named x and y. The 5 sublists are:
usr |
The coordinates of the input points in usr (User) coordinates. |
plt |
The coordinates of the input points in plt (Plot) coordinates. |
fig |
The coordinates of the input points in fig (Figure) coordinates. |
dev |
The coordinates of the input points in dev (Device) coordinates. |
tdev |
The coordinates of the input points in tdev (Total Device) coordinates. |
You must provide both x and y, but one of them may be NA.
This function is becoming depricated with the new functions
grconvertX and grconvertY in R version 2.7.0 and beyond.
These new functions use the correct coordinate system names and have
more coordinate systems available, you should start using them instead.
Greg Snow greg.snow@imail.org
old.par <- par(no.readonly=TRUE) par(mfrow=c(2,2),xpd=NA) # generate some sample data tmp.x <- rnorm(25, 10, 2) tmp.y <- rnorm(25, 50, 10) tmp.z <- rnorm(25, 0, 1) plot( tmp.x, tmp.y) # draw a diagonal line across the plot area tmp1 <- cnvrt.coords( c(0,1), c(0,1), input='plt' ) lines(tmp1$usr, col='blue') # draw a diagonal line accross figure region tmp2 <- cnvrt.coords( c(0,1), c(1,0), input='fig') lines(tmp2$usr, col='red') # save coordinate of point 1 and y value near top of plot for future plots tmp.point1 <- cnvrt.coords(tmp.x[1], tmp.y[1]) tmp.range1 <- cnvrt.coords(NA, 0.98, input='plt') # make a second plot and draw a line linking point 1 in each plot plot(tmp.y, tmp.z) tmp.point2 <- cnvrt.coords( tmp.point1$dev, input='dev' ) arrows( tmp.y[1], tmp.z[1], tmp.point2$usr$x, tmp.point2$usr$y, col='green') # draw another plot and add rectangle showing same range in 2 plots plot(tmp.x, tmp.z) tmp.range2 <- cnvrt.coords(NA, 0.02, input='plt') tmp.range3 <- cnvrt.coords(NA, tmp.range1$dev$y, input='dev') rect( 9, tmp.range2$usr$y, 11, tmp.range3$usr$y, border='yellow') # put a label just to the right of the plot and # near the top of the figure region. text( cnvrt.coords(1.05, NA, input='plt')$usr$x, cnvrt.coords(NA, 0.75, input='fig')$usr$y, "Label", adj=0) par(mfrow=c(1,1)) ## create a subplot within another plot (see also subplot) plot(1:10, 1:10) tmp <- cnvrt.coords( c( 1, 4, 6, 9), c(6, 9, 1, 4) ) par(plt = c(tmp$dev$x[1:2], tmp$dev$y[1:2]), new=TRUE) hist(rnorm(100)) par(fig = c(tmp$dev$x[3:4], tmp$dev$y[3:4]), new=TRUE) hist(rnorm(100)) par(old.par)
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