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I got this code which create two vectors and for each element from a I want to get the closest element in b :
a = rnorm(100)
b = rnorm(100)
c = vapply(a, function(x) which.min(abs(b - x)), 1)
table(duplicated(c))
FALSE TRUE
61 39
As you can see this method is prompt to give a lot of duplicates which is normal but I would like to not have duplicates. I thought of deleting occurence from b once an index has been selected but I don't know how to do it under vapply.
857
The closest () method searches up the DOM tree for the closest element which matches a specified CSS selector. It starts at the element itself, then tests the parent, grandparent, and so on until a match is found. If a match is not found, this method returns null .
We pick an outer element one by one. For every picked element, we traverse remaining array and find closest greater element. Time complexity of this solution is O (n*n)
Yes, though you could hand it all points at once as well. Per default query returns the closest vector in A to the given one. And it returns the distance to that vector and the position of the closest vector in A.
To compute the closest value in a vector “N” for each element of “V”, try the following code with example vectors “N” and “V”: Note that if there is a tie for the minimum value in each column, MATLAB chooses the first element in the column.
The closest match you are going to get is by sorting the vectors and then pairing them off. The following permuation on b should allow you to do that.
p <- order(b)[order(order(a))] # order on b and then back transform the ordering of a
sum(abs(a-b[p]))
[1] 20.76788
Clearly, allowing duplicates does make things much closer:
sum(abs(a-b[c]))
[1] 2.45583
This is very bad programming, but may work and is vectorized...
a <- rnorm(100)
b <- rnorm(100)
#make a copy of b (you'll see why)
b1<-b
res<- vapply(a, function(x) {ret<-which.min(abs(b1 - x));b1[ret]<<-NA;return(ret)}, 1)
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