MATLAB Answers


calculate distance using the below equation

Asked by Elysi Cochin on 11 Apr 2013
Accepted Answer by Matt J

i have 2 variables, dataMatrix and queryMatrix..... dataMatrix contains 245 rows and 38 column values...... and queryMatrix contains 1 row and 38 column values...... i calculate the euclidean distance and sort the distances in ascending order as below.....

    for w=1:245
        dist = sum((repmat(queryMatrix(w,:),245,1)-dataMatrix).^2,2);
        [sortval sortpos] = sort(dist,'ascend');
        neighborIds(w,:) = sortpos(1:k);
        neighborDistances(w,:) = sqrt(sortval(1:k));

instead of euclidean distance i want to use the distance formula in the below link.....

but i dont know to write the equation in matlab...... please can someone convert that equation to matlab..... it would be great help to me..... please do reply......

  1 Comment

Matt J
on 11 Apr 2013

If queryMatrix only has 1 row, how can w run from 1 to 245 in queryMatrix(w,:)?



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2 Answers

Answer by Matt J
on 11 Apr 2013
 Accepted answer

Assuming queryMatrix and dataMatrix are both 245x38, the whole thing can be done without loops,

    num = abs(bsxfun(@minus,d,q));
    den =  bsxfun(@plus,abs(d),abs(q));
    [sortval sortpos] = sort(dist);
    neighborIds = sortpos(1:k,:);
    neighborDistances = sqrt(sortval(1:k,:));


sir what is 1,3,2 and 3,2,1 in


shud i use it in my datavalues???..... as my datavalues are not of the same row and column values.... what changes should i make when i use for loop?? please do reply sir....

Matt J
on 11 Apr 2013

To understand the syntax of the PERMUTE command, see

 doc permute
 help permute

As I mentioned, you don't need to be using a for-loop. The only requirement here is that dataMatrix and queryMatrix have the same number of columns.

Answer by Andrei Bobrov
on 11 Apr 2013
Edited by Andrei Bobrov
on 11 Apr 2013

dataMatrix = randi([-10,10],10,5);
queryMatrix = randi([-10 10],1,5);
d = bsxfun(@(x,y)abs(x - y)./(abs(x) + abs(y)),...
                                         dataMatrix,permute(queryMatrix,[3 2 1]));
d = sort(squeeze(sum(d,2)));


sir in my code should i use for loop??? because when i do without for loop i'm getting all values NaN......

 dataMatrix = dataMatrix.*sign(rand(size(dataMatrix)));
 queryMatrix = queryMatrix.*sign(rand(size(queryMatrix))-.5);

shud i use this rand function for my set of values??

thank u all...

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