[R] modify rectangle color from image
marc_schwartz at comcast.net
Wed Jan 24 23:31:53 CET 2007
On Wed, 2007-01-24 at 16:37 -0500, Saurav Pathak wrote:
> I need some suggestion on how I could modify the color on some
> rectangle that I have created using "image".
> In other words, I have a 5x5 matrix, say, m.
> m <- matrix(rnorm(25), nrow=5)
> I create a grid of rectangles by:
> Now I want to change the color of rectangle (3,3) to blue.
> I don't know how this could be done, and searching the web has given
> me no hint.
> Thanks for your help.
m <- matrix(rnorm(25), nrow = 5)
# Get the plot region coords
USR <- par("usr")
# Calc the length of a side of a square
SIDE <- abs(USR - USR) / 5
# Draw the rect using the appropriate offsets
rect(USR + (SIDE * 2), USR + (SIDE * 2),
USR + (SIDE * 3), USR + (SIDE * 3), col = "blue")
See ?par and review "usr", then see ?rect
par("usr") gives you the coordinates of the plot region. Then just do
the math to calculate the coordinates of each rectangle.
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