Nearest Neighbors
Actually if you are looking for neighbors of neighbors you only need the nearest neighbor for each point. The problem is that the nearest neighbor of the nearest neighbor of point 1 is often point 1. Did you want the nearest neighbor not counting any point twice? Sounds more like a traveling salesman problem or nearest link cluster analysis.
set.seed(42) x <- rnorm(100, 50, 15) y <- rnorm(100, 50, 15) dat <- cbind(x, y) library(spdep) nn <- knearneigh(dat, 1) nn1 <- nn$nn # Nearest neighbors nn2 <- nn1[nn1] # Nearest neighbor of the nearest neighbor nn3 <- nn2[nn1] # Third order nn4 <- nn3[nn1] # Fourth order head(cbind(nn1, nn2, nn3, nn4), 10)
nn2 nn3 nn4 [1,] 53 1 53 1 [2,] 34 2 34 2 [3,] 67 3 67 3 [4,] 35 60 46 60 [5,] 82 5 82 5 [6,] 10 6 10 6 [7,] 48 7 48 7 [8,] 40 8 40 8 [9,] 25 9 25 9 [10,] 6 10 6 10 ---------------------------------------------- David L Carlson Associate Professor of Anthropology Texas A&M University College Station, TX 77843-4352
-----Original Message----- From: r-help-bounces at r-project.org [mailto:r-help-bounces at r- project.org] On Behalf Of Petr Savicky Sent: Sunday, July 29, 2012 1:44 PM To: r-help at r-project.org Subject: Re: [R] Nearest Neighbors On Tue, Jul 24, 2012 at 09:26:49AM -0700, olemissrebs1123 wrote:
I was wondering if there is a way in R to find k nearest neighbors of
various
orders, say order 2, 3, or 4. In otherwords neighbors of neighbors of neighbors. You get the idea. I know that I can use
knearneigh(matrix.data,
k) but this only gives me the k nearest neighbors and not of a
particular
order.
Hi. If i understand correctly, then this may be achieved by several iterations. In the first iteration, the nearest neighbours are found. The next iteration starts from them a finds their nearest neighbours. These are neighbours of order 2. A general iteration finds neighbours of order n by looking for neighbours of the points found in the previous step, which are the neighours of order n-1. Hope this helps. Petr Savicky.
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