[R] comparison of two vectors

Ben Bolker bolker at ufl.edu
Tue Dec 4 20:57:09 CET 2007




Daniel Stepputtis wrote:
> 
> Dear Ben,
> I was searching for the same problem. Thank you very much, it helped me a
> lot and I will use it quite often!
> 
> In addition to the problem given by tintin_et_milou. I have to compare a
> two pairs of vectors.
> 
> I.e. I have two datasets each with latitude and longitude (which defines
> the geographical position of data points.)
> As you might imagine, it is meaningful to take into account both latitude
> and longitude, when searching for the nearest data point from the otehr
> dataset.
> 
> Do you have any idea how to do this efficiently (actually I used loops ;-(
> ?
> Best regards
> Daniel
> 
> 
> Ben Bolker schrieb:
>> 
>> distfun <- function(x1,x2) { (x1-x2)^2 }
>> 
>> outer(m1[,1],y,distfun)
> 
>>   cheers
>>     Ben
> 

  Maybe (untested)

  distfun <- function(i,j) { (x1[i]-x2[j])^2 + (y1[i]-y2[j])^2) }
outer(i,j,distfun)

  ?
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