[R] Artifacts in pdf() of image()
Michael Kubovy
kubovy at virginia.edu
Sat Aug 11 22:31:23 CEST 2007
Dear r-helpers,
I have two questions:
(1) The following produces a pdf with artifacts. How do I prevent them?
require(grDevices)
imSize <- 200
lambda <- 10
theta <- 15
sigma <- 40
x <- 1:imSize
x0 <- x / imSize -.5
freq = imSize/lambda # compute frequency from
wavelength
xf = x0 * freq * 2 * pi # convert X to radians: 0 ->
( 2*pi * frequency)
f <- function(x, y){r <- -((x^2 + y^2)/(sigma ^2)); exp(r)}
z <- outer(xf, xf, f)
f1 <- function(x, y){cos(.1 * x)}
z1 <- outer(xf, xf, f1)
pdf('gabor.pdf')
image(xf, xf, z * z1, col = gray(250:1000/1000), xlab = '', ylab =
'', bty = 'n',
axes = FALSE, asp = 1)
dev.off()
(2) I would like the output to be clipped to a circle, i.e., anything
outside the circle tangent to the sides of the square should be
transparent. How can I do that?
_____________________________
Professor Michael Kubovy
University of Virginia
Department of Psychology
USPS: P.O.Box 400400 Charlottesville, VA 22904-4400
Parcels: Room 102 Gilmer Hall
McCormick Road Charlottesville, VA 22903
Office: B011 +1-434-982-4729
Lab: B019 +1-434-982-4751
Fax: +1-434-982-4766
WWW: http://www.people.virginia.edu/~mk9y/
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