[R] problem with outer and image

[Peter Dalgaard BSA]

Bill Simpson <wsi at gcal.ac.uk> writes:

> I want to make a picture of a cos wave grating (pattern of fuzzy stripes).
> First I try to make a plot of a cos wave:
> x<-seq(1:100)
> y<- 10*cos(2*pi*x*3/length(x)+0)+300
> plot(x,y)
> That works fine. 3 cycles of cos wave. Now try for grating.
> 
> time<-seq(1:100)
> f<-function(x,time) 10*cos(2*pi*x*3/length(x)+0)+300
> z<-outer(x,time,f)
> image(x,time,z)
> I get a vertical grating as expected, BUT now I get <1 cycle of cos
> wave. Varying the frequency (3 above) does nothing. I don't understand
> what I am doing wrong.

length(x) == 100 in the 1st case, == 1 in the 2nd. 

BTW: seq(1:100) is a bad idea. Try seq(99:100) to see why. Or seq(10:10).

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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