How to find minimal distance during locomotion

Hello,

I would like to find the distance between two points. I have a dataset with 4 columns , the first and second column are the x,y coordinates for the participants locomotion, the third and fourth columns are the X,Y coordinates for the targets (total targets =9, ). I would like to know if the participant reached a target or several targets during de locomotion using the distance. I wrote this function :

function d= distini(x,X,y,Y)

    for i=1:length(x)
        for ii=1:9
           t= sqrt(((X(ii) - x(i)).^2) + ((Y(ii)- y(i)).^2));
           d=t'
        end
    end 
end 
thanks in advance

[Jan]

What is your question?

Your t is a scalar, so there is no effect in transposing it.

Answer 1

[Jan]

I'm not sure, what you are asking for. So just a guess:

function d = distini(x,X,y,Y)
d = zeros(numel(X), numel(x));
X = X(:);  % If X and Y are not column vectors
Y = Y(:);
for k = 1:numel(x)
    d(:, k) = sqrt((X - x(k)) .^ 2 + (Y - y(k)) .^ 2);
end 
end

Does this help?

[Alex castilla]

Thanks for your reply.

Just for clarification: The x, y represent two columns vectors which is the participant trajectory coordinates x,y . The capital X,Y are columns vectors of the coordinates of nine targets. I would to calculate the distance between the trajectory and the targets.

bearing in mind these modifications, is my function correct?

function d = distini(x,X,y,Y)

d = zeros(numel(x));

    for k = 1:numel(x)

        for n= 1:9

        d(:, k) = sqrt((X(n) - x(k)) .^ 2 + (Y(n) - y(k)) .^ 2);

end

end

end

[Jan]

I assume you want

d = zeros(9, numel(x));
...
     d(n, k) = ...

or exactly the code I have posted already.

d = zeros(numel(x));

This would create a a [numel(x) * numel(x)] matrix, but I think you want a [9 * numel(x)] matrix as output.

This creates a scalar:

sqrt((X(n) - x(k)) .^ 2 + (Y(n) - y(k)) .^ 2);

but you assign it to the vector d(:, k). This works, but overwrite all values by the scalar in each iteration.

I use the terms "not sure", "guess", "assume" and "think", because you did not clarify exactly, what you want to achieve. The description is not clear enough:

 I would like to know if the participant reached a target or several
 targets during de locomotion

Do you see, that your code looks more scrambled than the one I post? I'm selecting the code with the mouse and press the "{} Code" button to format it properly.

[Alex castilla]

Thanks for your answers. I would like to clarify:

I have two matrices: A(2099x2) and B(9x2).

Matrix A = trajectory (x,y)

Matrix B = position of 9 targets ( X,Y)

I would like to know how to calculate the distance (red arrows) of the nearest-neighbor of a point between the trajectory (blue line) and the targets( red squares). Thanks in advance

[Jan]

A = rand(2099, 2);
B = rand(9, 2);

D = zeros(9, 1);
for k = 1:9
   dist = (A(:, 1) - B(k, 1))^2 + (A(:, 2) - B(k, 2))^2;
   D(k) = sqrt(min(dist));
end

Now D(k) contains the minimal distance of the trajectory in A to B(k).

[Alex castilla]

Thanks so much