From: Pete on
I think I see - however, X and Y form circles of points......each column of X and Y (from left to right) roughly forms a circle of points (using positive and negative coordinates)....as the columns of coordinates go from left to right, the radii of the circles increases.........and the radii do not increase by a constant amount from column to column. Probably i am missing the point, but i can't see a way to simply add on and divide etc. to change the random walk coordinates (x,y) so that they lie between 1:nrp and map to such a spatial grid in a meaningful way.

ImageAnalyst <imageanalyst(a)mailinator.com> wrote in message <ede0ad28-c333-4083-82c4-420434440c4c(a)t42g2000vba.googlegroups.com>...
> Pete:
> Yes I realized that. And I thought my last paragraph was the nice
> "trick" that would speed it up for you.
>
> Why calculate the min of a huge bunch of numbers, and then compare it
> to that same bunch of numbers just to find an index that you already
> have? And then you do this unnecessary stuff not once, but twice.
> And it's not only twice, it's twice for every one of your ten thousand
> numbers - what a huge waste of time and effort for something that can
> be done so simply and efficiently.
> -ImageAnalyst
From: Pete on
I think I see - however, X and Y form circles of points......each column of X and Y (from left to right) roughly forms a circle of points (using positive and negative coordinates)....as the columns of coordinates go from left to right, the radii of the circles increases.........and the radii do not increase by a constant amount from column to column. Probably i am missing the point, but i can't see a way to simply add on and divide etc. to change the random walk coordinates (x,y) so that they lie between 1:nrp and map to such a spatial grid in a meaningful way.

ImageAnalyst <imageanalyst(a)mailinator.com> wrote in message <ede0ad28-c333-4083-82c4-420434440c4c(a)t42g2000vba.googlegroups.com>...
> Pete:
> Yes I realized that. And I thought my last paragraph was the nice
> "trick" that would speed it up for you.
>
> Why calculate the min of a huge bunch of numbers, and then compare it
> to that same bunch of numbers just to find an index that you already
> have? And then you do this unnecessary stuff not once, but twice.
> And it's not only twice, it's twice for every one of your ten thousand
> numbers - what a huge waste of time and effort for something that can
> be done so simply and efficiently.
> -ImageAnalyst
From: ImageAnalyst on
What's wrong with the way I suggested? You basically send out a bunch
of random paths. Then you want to calculate a histogram of the number
that stop at various radii, right? Why then have a 2D histogram? Why
not just histogram along distance? If, instead, you want a histogram
(count) of how many stop at each 2D coordinate (because radius alone
is not enough, and you need direction also), then you can use a 2D
array and use the method I suggested to increment the number that stop
at each location.
From: Pete on
Hi ImageAnalyst:
What I need to do is calculate how many points stop at each 2D coordinate.
Imagine the radii of the circles that X and Y produce increase like so:
r = [0.1 2 13 200 7000 36000 50000.......etc], so we have a bunch of X and Y coordinates covering a whole host of magnitudes, that are non-uniformly spaced, and positive and negative.
How can I obtain the index of random walk coordinates in order to map them to an X and a Y in such a radically non-uniform grid by just adding on a number and dividing by another? If that's possible, I seem to be missing a piece.........
Cheers
Pete



ImageAnalyst <imageanalyst(a)mailinator.com> wrote in message <78bb22bc-1649-4e5a-a945-c185a5d4d75d(a)o28g2000yqh.googlegroups.com>...
> What's wrong with the way I suggested? You basically send out a bunch
> of random paths. Then you want to calculate a histogram of the number
> that stop at various radii, right? Why then have a 2D histogram? Why
> not just histogram along distance? If, instead, you want a histogram
> (count) of how many stop at each 2D coordinate (because radius alone
> is not enough, and you need direction also), then you can use a 2D
> array and use the method I suggested to increment the number that stop
> at each location.