Matrix that changes size

I need to create a matrix that changes sizes. The user inputs x and y coordinates and then I want to display them as a matrix, but the number of coordinates changes. This is the code i have so far, where NJ=number of x and y coordinates the user inputs and then they input the coordinates:

disp('Part I: Input Joint Data');

NJ=input('Enter Number of Joints, NJ = ');

for I=1:NJ

fprintf('\nEnter coordinate of joint %d\n', I);

COORD(I,1)=input('X coordinates = ');

COORD(I,2)=input('Y coordinates = ');

x=COORD(I,1);

y=COORD(I,2);

end

how do i create the matrix? thanks in advance

Answer 1

[David Hill]

why not enter them all at once?

m=input('input x and y coordiants in a matrix, as an example [1 2;3 4;5 6]: ');

Answer 2

[Voss]

One thing you can do is to pre-allocate COORD to be the correct size after NJ is input by the user. (And if this code is used inside a loop, then you won't have the problem of COORD having too many rows when NJ decreases from one iteration of the loop to the next.)

disp('Part I: Input Joint Data');
NJ=input('Enter Number of Joints, NJ = ');

% create a matrix of the correct size, of all zeros:
COORD = zeros(NJ,2);

for I=1:NJ
    fprintf('\nEnter coordinate of joint %d\n', I);
    COORD(I,1)=input('X coordinates = ');
    COORD(I,2)=input('Y coordinates = ');
    x=COORD(I,1);
    y=COORD(I,2);
end