On Sep 24, 2015, at 1:54 PM, Lorenzo Isella wrote: > On Thu, Sep 24, 2015 at 01:30:02PM -0700, David Winsemius wrote: >> >> On Sep 24, 2015, at 12:36 PM, Lorenzo Isella wrote: >> >>> Hi, >>> And thanks for your reply. >>> Essentially, your script gets the job done. >>> For instance, if I run >>> >>> mm <- cbind(5/(1:5), -2*sqrt(1:5)) >>> dst <- dist(mm) >>> dst2 <- as.matrix(dst) >>> diag(dst2) <- NA >>> idx <- which(apply(dst2, 1, function(x) all(na.omit(x)>.9))) >>> >>> then it correctly detects the first two rows, where all the values are >>> larger than 0.9. >>> In other words, it detects the points that are at least 0.9 units away >>> from *all* the other points. >>> My other question (I did not realize this until I got your answer) is >>> the following: I have the distance matrix of a set of N points. >>> You gave me an algorithm two find all the points that are at least 0.9 >>> units away from any other points. >>> However, in some cases, for me it is OK even a weaker condition: find >>> a subset of k points (with k tunable) whose distance *from each other* >>> is greater than 0.9 units (even if their distance from some other >>> points may be smaller than 0.9). >> >> If I understand ..... Make a matrix of unique combinations, then apply by >> rows to get the qualifying columns that satisfy the distance criterion: >> >> mtxcomb <- combn(1:20, 5) >> goodcls <- apply(mtxcomb , 2, function(idx) all( dist( cbind( x[idx], >> y[idx]) ) > 0.9)) >> mtxcomb [ , goodcls] >> >> In my sample it was around 9% of the total 5 item combinations. >> >> snipped a lot of output: >> ..... >> [,1440] [,1441] >> [1,] 12 13 >> [2,] 13 16 >> [3,] 16 17 >> [4,] 19 19 >> [5,] 20 20 >>> dim( mtxcomb) >> [1] 5 15504 >> > > Hi, > Thanks for your reply. > I think I am getting there, but when I run your commands, I get this > error message > > Error in cbind(x[idx], y[idx]) : object 'x' not found > > Any idea why? Should I combine those 3 lines with something else?
No idea. I was running the setup that you asked for in your original message which you have now omitted from the mail chain. > Cheers > > Lorenzo David Winsemius Alameda, CA, USA ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
