On Aug 12, 2007, at 6:24 AM, Duncan Murdoch wrote:
> Michael Kubovy wrote:
>> Dear r-helpers,
>>
>> In my previous message there were comments in the code that may
>> have made cutting and pasting awkward. Here it is w/o them.
>>
>> I have two questions:
>>
>> (1) The following produces a pdf with artifacts. How do I prevent
>> them?
>>
>
> What artifacts do you see? It looks like a smoothly varying field
> when produced by R 2.5.1 and viewed in Acrobat Reader 6.0 on Windows.
>
> Duncan Murdoch
>> require(grDevices)
>> imSize <- 200
>> lambda <- 10
>> theta <- 15
>> sigma <- 40
>> x <- 1:imSize
>> x0 <- x / imSize -.5
>> freq = imSize/lambda
>> xf = x0 * freq * 2 * pi
>> 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()
I'm working on a Mac. You're right, Acrobat 6.05 renders the figure
nicely, but when it's included in a LaTeX-produced pdf or viewed with
the Mac Preview program, a grid of fine white lines is superimposed
on the figure. So I believe that it's a matter of aliasing, which I
might be able to prevent by adjusting the parameters of the figures.
I just don't know enough to figure this out, and would appreciate
guidance.
_____________________________
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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