Error in array bounds

clc; clear all; close all;
load('bunny.mat')
 
 
%% Visualize PC
figure;
scatter3(P(1,:), P(2,:), P(3,:),10,Color,'filled');
xlabel('x axis');
ylabel('y axis');
zlabel('z axis');
 
%% Problem 1:
title('bunny1');
saveas(gcf, "bunny1");
 
 
for sx=0.01:5
    P = [];
    s = [sx, 0, 0;
         0, sx, 0;
         0, 0, sx];
    for i = 1:2396
        pi = P(:,i);
        spi = s * pi;
        P = [SP,spi];
    end
   figure;
scatter3(P(1,:), P(2,:), P(3,:),10,Color,'filled');
xlabel('x axis');
ylabel('y axis');
zlabel('z axis'); 
end

Below is not part of the code

*color is 1x2396 and P is 3x2396

Why do I get the error "Index in position 2 exceeds array bounds.

Error in script (line 23)

pi = P(:,i);"? and how do I fix it?

Answer 1

[Walter Roberson]

"P is 3x2396"

No it is not. You assign [] to P.

[Midlij]

let's suppose that it is 3x2396. How do I fix the error?

Answer 2

[DGM]

% ...

% this loop has been simplified to the point that it works
% for sx = 0.01:5
%     s = [sx, 0, 0;
%         0, sx, 0;
%         0, 0, sx];
%     
%     for k = 1:size(P,2)
%         P(:,k) = s * P(:,k);
%     end
% end

% but it's needlessly roundabout, because it simplifies to 
P = P*4.01;
% which is probably not what you want, but you haven't described that.

scatter3(P(1,:), P(2,:), P(3,:),10,Color,'filled');
xlabel('x axis');
ylabel('y axis');
zlabel('z axis');

[Midlij]

I tried the code, but it is not providing me with the required values when the figures are displayed. What could have gone wrong?

[DGM]

Nobody knows, because nobody else knows what the required values are.

The only information you provided was nonfunctioning code which appears to do what I demonstrated. You're multiplying each point by the identity matrix (multiplied by a scalar sx). As the name "identity matrix" implies, the result is the point itself multiplied by sx. Since the results are overwritten each time the loop iterates, the result is P multiplied by the last value of sx, which is 4.01. You could plot the points each time...

% ...

for sx = 0.01:5
    Ps = P*sx;
    scatter3(Ps(1,:), Ps(2,:), Ps(3,:),10,Color,'filled'); hold on
end

xlabel('x axis');
ylabel('y axis');
zlabel('z axis');

If the code is supposed to do something else, then you'll have to clearly describe what that is.