The updateusr method from Greg Snow's TeachingDemos package is a great solution for this problem. The idea behind updateusr is define new plot region according to the ratio of one unit in each axis.
The code:
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| updateusr <- function(x1, y1=NULL, x2, y2=NULL) { | |
| xy1 <- xy.coords(x1,y1) | |
| xy2 <- if( missing(x2) && missing(y2) ) { | |
| xy.coords(y1) | |
| } else { | |
| xy.coords(x2,y2) | |
| } | |
| cur.usr <- par('usr') | |
| xslope <- diff(xy2$x)/diff(xy1$x) | |
| yslope <- diff(xy2$y)/diff(xy1$y) | |
| new.usr.x <- xslope * ( cur.usr[1:2] - xy1$x ) + xy2$x | |
| new.usr.y <- yslope * ( cur.usr[3:4] - xy1$y ) + xy2$y | |
| invisible(par(usr=c(new.usr.x, new.usr.y))) | |
| } |
Example code:(add space 8/20)
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| yy <- c(4,6,13,24,15,13,14,8,2,1) | |
| n <- length(yy) | |
| bar <- data.frame(Group=LETTERS[1:n], value=yy*1000, yield=yy+rnorm(n,50,10)) | |
| ylim <- c(0,max(bar$value)) | |
| space <- 0.3 | |
| xlim <- c(0, floor((1+space)*n)+1) | |
| plot(0, xaxs = "i", xlim = xlim, ylim = ylim, main = "Barplot with Line use par(new=TRUE)", xlab = "", ylab = "", type = "n", axes = FALSE) | |
| r <- barplot(bar$value, axes=F, axisnames = FALSE, space = space, add = T) | |
| axis(1, at = r, labels = LETTERS[1:n]) | |
| axis(2, at = seq(0,ylim[2], 1000), las = 2) | |
| #use par new | |
| par(new = TRUE) | |
| plot(x = r, y = bar$yield, axes = FALSE, xlim = xlim, ylim = c(0,110) ,xlab = "", ylab = "",type = "o") | |
| abline(v=r, lty = 2, col = "red") | |
| axis(4, at = seq(0, 110, 10)) | |
| box() | |
| plot(0, xaxs = "i", xlim = xlim, ylim = ylim, main = "Barplot with Line use updateusr", xlab = "", ylab = "", type = "n", axes = FALSE) | |
| r <- barplot(bar$value, axes=F, axisnames = FALSE, space = space, add = T) | |
| axis(1, at = r, labels = LETTERS[1:n]) | |
| axis(2, at = seq(0,ylim[2], 1000), las = 2) | |
| #By using updateusr | |
| updateusr(r[1:2], ylim/100, r[1:2], 0:1) | |
| lines(x = r, y = bar$yield, type = "o") | |
| abline(v=r, lty = 2, col = "red") | |
| axis(4, at = seq(0, 110, 10)) | |
| box() |
Result:
