How can I save the x and y values obtained from ginput through a for loop?

I am working on a problem that requires for me to save an N by M text file containing the content of each box in a grid that is over an image. I created a GUI where the user clicks over the image and a marker (square) is plotted. I am trying to save all the x & y values to determine where on the grid there is a filled box, but since I am using a for loop, the values are replaced each time. I tried creating an empty matrix and storing the values in the matrix but only one set of values is stored. Does anyone have suggestions on how to go about this? This is part of my code:

switch pp case 1

    case 2
        hold on
        [x,y]=ginput(1);
        X=[];
        for i=1:x_len 
            if x>x_vals(i) && x<x_vals(i+1)
                x=2*x_mid(i)+10;

                X=[i];

            end 

        end

        Y=[];
        for j=1:y_len
            if y>y_vals(j) && y<y_vals(j+1) 
                y=2*y_mid(j)+10;
                Y=[j];
            end 
        end 
       plot(x,y,'s','LineWidth',1,...
                'MarkerEdgeColor','r',...
                'MarkerFaceColor','r',...
                'MarkerSize',6)

            hold off

Answer 1

[Azzi Abdelmalek]

data(k,:)=ginput(1);
x=data(k,1)
y=data(k,2)

[Ilse]

I tested this but got an error saying k was undefined.

[Azzi Abdelmalek]

At the beginning of your code, initialize data

data=[]

then add

data(end+1,:)=ginput(1);
x=data(k,1)
y=data(k,2)