Vectorizing Array -- Wrong Dimensions?

Hi all, I'm a native C programmer and am having a hard time understanding Matlab's behavior.

I have three arrays:

sample.currtargdist (2252 x 1)
sample.targloc (1 x 2552)
distance (6 x 2252)

I can't figure out why this code results in a 2252 x 2252 matrix:

for s = 1:setsize;
    distance(s,:) = sqrt((sample.RIGHT_GAZE_X-loc(s).x).^2+(sample.RIGHT_GAZE_Y-loc(s).y).^2);
end
sample.currtargdist = distance(sample.targLoc,:);

When I try something like a '1' instead of ':', I just get the first column of the matrix. I want just the first row of the output matrix.

[Azzi Abdelmalek]

This is not clear, what is sample.RIGHT_GAZE_X-loc? what is the value of setsize?

[Nick G]

it's a measure of eyegaze position. It's in a 1 x 2552 array. Set size is 6. I'm measuring the distance of eyegaze from items on a screen.

[Jan]

Which one is "the output matrix"?

[Nick G]

sample.targcurrdist

[Nick G]

sample.targloc is an index that can be used to tell which distance value to pull

[Stephen23]

What are sample.RIGHT_GAZE_X, sample.RIGHT_GAZE_Y, setsize, loc.x and loc.y? If they are variables, what sizes are they?

"this code results in a 2252 x 2252 matrix": which variable is the output?

Answer 1

[Jan]

 I want just the first row of the output matrix.

Perhaps you mean this:

sample.currtargdist = distance(sample.targLoc(1), :);

If targLoc has the size 1 x 2552 and distance is 6x2552, then distance(targloc,:) is expected to be 2552x2552 - or a bug, if the elements of targloc exceed the values 1:6.

Answer 2

[Azzi Abdelmalek]

Probably, the value of setsize is 2252, or maybe in your code, you have pre-allocated the variable distance with zeros(2252,2252)