Thanks for the quick answer Tom. Carlos
On Thu, Feb 21, 2008 at 3:52 PM, Tom Russo <[EMAIL PROTECTED]> wrote: > On Thu, Feb 21, 2008 at 03:11:43PM -0300, we recorded a bogon-computron > collision of the <[EMAIL PROTECTED]> flavor, containing: > > > Yes, Eric, that is what it does for a _square_ neighborhood. I am a > > little confuse about the actual shape of the _circular_ neighborhood. > > > > using your examples: > > > > will a 3x3 circular neighborhood look like this:? > > > > ---o--- > > o-X-o > > ---o--- > > > > and a 5x5? > > > > ---o-o-o--- > > o-o-o-o-o > > o-o-X-o-o > > o-o-o-o-o > > ---o-o-o--- > > > > > > maybe now my question is more clear... > > Piping in here after a quick glance at the source code... > > When the "-c" option to r.neighbors is selected, a neighborhood mask of > booleans > is created by this loop (in pseudocode): > > neighborhoodDistance=neighborhoodSize/2 (in integer math) > for (i=0; i<neigborhoodSize; i++) > for (j=0; j<neighborhoodSize; j++) > mask[i][k]= ( (i-neighborhoodDistance)^2 + (j-neighborhoodDistance)^2 > <= (neighborhoodDistance)^2 > > So in a 3x3 example, neighborhoodSize=3, neighborhoodDistance=1, and your > first diagram has "o"s where the mask is true. The corners of the square > wouldn't be in the mask (as in Eric's 3x3), because those points would have > the left hand side of the inequality equal to 2, making the mask false. > > I haven't actually *tried* the code, but that is what the block of code in > gather.c for circular neighborhoods says it should be doing. > > > > > > >I was thinking about the circular neighborhoods that r.neighbors use. > > > >How exactly are they shaped? I mean, in a 3x3 window, does the > > > >circular one looks like a cross? and then it start to look more like a > > > >circle as the size increases? > > > > > > As far as I understand it, > > > > > > A 3x3 window would look like this: > > > > > > o-o-o > > > o-X-o > > > o-o-o > > > > > > Where the 'X' is the current cell being processed. Similarly, a 5X5 > window > > > would look like this: > > > > > > o-o-o-o-o > > > o-o-o-o-o > > > o-o-X-o-o > > > o-o-o-o-o > > > o-o-o-o-o > > > > > > r.neighbors will perform calculations on all the cells I've marked 'o' > and and > > > assign the output value to 'X', according to whatever method has been > chosen > > > (i.e., average, median, min, max, etc.). > > > > > > ~ Eric. > > > > > > > > > > > -- > > +-----------------------------------------------------------+ > > Carlos Henrique Grohmann - Guano > > Geologist M.Sc - Doctorate Student at IGc-USP - Brazil > > Linux User #89721 - carlos dot grohmann at gmail dot com > > +-----------------------------------------------------------+ > > _________________ > > "Good morning, doctors. I have taken the liberty of removing Windows > > 95 from my hard drive." > > --The winning entry in a "What were HAL's first words" contest judged > > by 2001: A SPACE ODYSSEY creator Arthur C. Clarke > > > > Can't stop the signal. > > _______________________________________________ > > grass-user mailing list > > [email protected] > > http://lists.osgeo.org/mailman/listinfo/grass-user > > -- > Tom Russo KM5VY SAR502 DM64ux http://www.swcp.com/~russo/ > Tijeras, NM QRPL#1592 K2#398 SOC#236 AHTB#1 > http://kevan.org/brain.cgi?DDTNM > "And, isn't sanity really just a one-trick pony anyway? I mean all you get is > one trick, rational thinking, but when you're good and crazy, oooh, oooh, > oooh, the sky is the limit!" --- The Tick > -- +-----------------------------------------------------------+ Carlos Henrique Grohmann - Guano Geologist M.Sc - Doctorate Student at IGc-USP - Brazil Linux User #89721 - carlos dot grohmann at gmail dot com +-----------------------------------------------------------+ _________________ "Good morning, doctors. I have taken the liberty of removing Windows 95 from my hard drive." --The winning entry in a "What were HAL's first words" contest judged by 2001: A SPACE ODYSSEY creator Arthur C. Clarke Can't stop the signal. _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
