Hi again,
I've had a go at Prof Ripley's suggestion (Strauss process, code
below). It works great for my limited purpose (qualitative drawing,
really), I can just add a few mild concerns,
- ideally the hard core would not be a fixed number, but a
distribution of sizes (ellipses).
- I
Baptiste Augui? writes:
I have to generate a random set of coordinates (x,y) in [-1 ; 1]^2
for say, N points.
[...]
My problem is to avoid collisions (overlap, really) between the
points. I would like some random pattern, but with a minimum
exclusion distance.
As Brian Ripley has
Dear list useRs,
I have to generate a random set of coordinates (x,y) in [-1 ; 1]^2
for say, N points. At each of these points is drawn a circle (later
on, an ellipse) of random size, as in:
N - 100
positions - matrix(rnorm(2 * N, mean = 0 , sd= 0.5), nrow=N)
sizes-rnorm(N, mean = 0 ,
baptiste Auguié wrote:
Dear list useRs,
I have to generate a random set of coordinates (x,y) in [-1 ; 1]^2
for say, N points. At each of these points is drawn a circle (later
on, an ellipse) of random size, as in:
The quasi-random sequences are useful for integration, but they're not
On Sat, 26 Apr 2008, baptiste Auguié wrote:
Dear list useRs,
I have to generate a random set of coordinates (x,y) in [-1 ; 1]^2
for say, N points. At each of these points is drawn a circle (later
on, an ellipse) of random size, as in:
N - 100
positions - matrix(rnorm(2 * N, mean = 0 , sd=
You seem to have ambiguous requirements.
First, you want equidistribution for a packing
structure, which would suggest closest packing or
quasirandom sequences, as you have tried.
But then you are disturbed by the packing
structure, because it gives a perceivable
pattern, so you wish to
baptiste Auguié ba208 at exeter.ac.uk writes:
Dear list useRs,
You might be interested to apply the Hammersley or Halton point sets that
are often used in numerical integration or Differential Evolution. These
pseudo-random distributions are both uniform and irregular, but have a
kind of
Thank you all for the great suggestions and comments. As two of you
pointed out, the problem was not well defined (who said a well-posed
problem is a problem solved?), and also it seems to be a very wide
topic. I've had an interesting reading discussing the similarities
between half-toning
You might want to shuffle coordinates independently to get rid of the
diagonals. Otherwise what quasi-random sequence guarantee are upper
boundaries on the coverage errors, but not anything nice-looking and
irregular. Sobol' sequences, even though they are theoretically
superior to some others
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