Question

I have two arrays in matlab representing tracked points by two different methods. In each array the first column contains the frame number, and columns two and three are the x, y coordinates. The tracks don’t necessarily start or finish at the same frame, but I want to compare the distances between tracks for any common frames.

My input data is something along the lines of:

d1 =              d2 = 
[ 130 50 20;      [ 128 48 17;
  131 50 21;        129 52 19;
  ...               ...
  195 70 36 ]       180 65 34 ]

I can find intersecting frame numbers using

commonFrames = intersect(d1(:,1), d2(:,1));

but I’m stuck on how to align these arrays (preferably without a for loop)?

I’d looking for an output along the lines of [frameNumber x1 y1 x2 y2] where x1, y1 are values from frame frameNumber of array d1, and x2, y2 are values from frame frameNumber of array d2.

Answer 1

‘intersect’ function has two additional output values: indices of common values in input arrays.

Your script can be following:

[commonFrames,ia,ib] = intersect(d1(:,1), d2(:,1));
commonData = [commonFrames d1(ia,2:3) d2(ib,2:3)];