How to select a pixel on a figure and display linked data?

Starting from a matrix which contains only -1,0,+1 values, i compute distances between every positive point to 'tau' nearest negative ones. After i create an array of structures of this type:

mystruct(i).coord= [x y]   % coordinates of positive point
mystruct(i).nearest= [x y] % where x and y are column vectors representing x and         %y coordinates of 'tau' nearest points
mystruct(i).dist= d %d is a column vector with corresponding distance between i and one of tau nearest points.

Now, i want to display in a Figure the original matrix marking in different colors (ex red and blue)positive and negative points with the possibility of selecting one or more positives and showing marking with another color (ex green) the corresponding nearest neighbours. I guess i'll have to use a callback function associating it to ButtonDownFcn but i'm not so used to graphic function. Is there someone who can give me an help or just some links to better understand the procedure? Thanks in advance..

Answer 1

[Image Analyst]

Why can't you just use plot()?

plot(x1, y1, 'r+');
hold on;
plot(x2, y1, 'g+');

[Image Analyst]

Responding to your "Answer" below... Can you upload a screenshot of your desired appearance so we can see what you'd like? Mock up something in Photoshop if you have to.

Answer 2

[Giaime Origgi]

Using only plot i can display all positives and negatives but i can't visualize every 'tau' negative neighbours linked to one positives..

[Image Analyst]

Is this an answer? I think it should have been a comment to me rather than an answer to your original question.