I'm getting a matrix error of inconsistently on line 45, any tips how I can fix it.

N=10;
L=10;
D=.01;
dt=.01;
k_on=1;
k_off=.1;
F=1;
tmax=100;

x=L*rand(N,1);
y=L*rand(N,1);
state=zeros(N,1);

figure;
axis([0 L 0 L]);
set(gca,'nextplot','replacechildren');

for t = 0:dt:tmax
    dx=sqrt(2*D*dt)*randn(N,1);
    dy=sqrt(2*D*dt)*randn(N,1);

    x=x+dx;
    y=y+dy;

    x(x<0)=0;
    x(x>L)=L;
    y(y<0)=0;
    y(y>L)=L;
    p_on=k_on*dt*F;
    p_off=k_off*dt;

    for i = 1:N
        if state(i)==0
            if rand < p_on
                state(i)=1;
            end
        else
            if rand<p_off
                state(i)=0
            end
        end
    end
colors= repmat([1 0 0], N,1);
colors(state == 1,:,:) = repmat([0 1 0],sum(state),1);
scatter(x,y,50,colors,'filled');
title(sprintf('Time=%.2f',t));
drawnow;
if any(state == 1)
    p_bind=1-exp(-k_on*dt*F);
    if rand<p_bind
        [~,i]=max(state);
        state(i)=2;
        colors(i,:)=[0]
       
    end
end
end

colors = 10×3

1 0 0 1 0 0 1 0 0 1 0 0 0 0 0 1 0 0 1 0 0 1 0 0 0 1 0 0 1 0

Unable to perform assignment because the size of the left side is 2-by-3 and the size of the right side is 4-by-3.

[Walter Roberson]

What is the difference between this and https://www.mathworks.com/matlabcentral/answers/1955619-i-keep-getting-this-matrix-error-when-i-run-my-code-any-tips-how-i-can-fix-it-its-line-45?s_tid=srchtitle ?

Answer 1

[LeoAiE]

It seems there is an issue with the assignment of the colors variable in the last part of your code.

N=10;
L=10;
D=.01;
dt=.01;
k_on=1;
k_off=.1;
F=1;
tmax=100;
x=L*rand(N,1);
y=L*rand(N,1);
state=zeros(N,1);
figure;
axis([0 L 0 L]);
set(gca,'nextplot','replacechildren');
for t = 0:dt:tmax
    dx=sqrt(2*D*dt)*randn(N,1);
    dy=sqrt(2*D*dt)*randn(N,1);
    x=x+dx;
    y=y+dy;
    x(x<0)=0;
    x(x>L)=L;
    y(y<0)=0;
    y(y>L)=L;
    p_on=k_on*dt*F;
    p_off=k_off*dt;
    for i = 1:N
        if state(i)==0
            if rand < p_on
                state(i)=1;
            end
        else
            if rand<p_off
                state(i)=0
            end
        end
    end
    colors = repmat([1 0 0], N,1);
    colors(state == 1,:,:) = repmat([0 1 0],sum(state == 1),1);
    scatter(x,y,50,colors,'filled');
    title(sprintf('Time=%.2f',t));
    drawnow;
    if any(state == 1)
        p_bind=1-exp(-k_on*dt*F);
        if rand<p_bind
            [~,i]=max(state);
            state(i)=2;
            colors(i,:)=[0 0 1]; % Corrected color assignment
        end
    end
end

[BAILEY MCMASTER]

I tried this and I'm still getting the matrix error after running it.

[BAILEY MCMASTER]

Actually nevermind, one of my ends was in the wrong spot, it works. Thank you so much!