Matrix does not agree

Help. I am about to pull my hair out. Not sure how to fix this error i keep having. Here is the code.

Error using  .* 
Matrix dimensions must agree.

Error in p2_1 (line 36)
      u_trans = e.*wave*A(n);  %  u(x,t) term calculation

clc;
clear;

p=100;

% --Grid--
xgrid = linspace(0,1,p);
tgrid = linspace(0,0.5,p);
[x,t] = meshgrid(xgrid,tgrid);

A = linspace(0,0,p);
u = zeros(p,p);
x = linspace(0,1,p);

%--Computation of An Terms--
n=1;
I=1;

while n==2
    I=0.5;
    if n<=p
        I = -(4*sin((pi*n)/2))/(pi*(n^2 - 4));
    end
    A(n)= A(n) + I;
end

% --Approx the solution--
e=linspace(0,1,p);
wave=linspace(0,1,p);
 while n <= p
      exponent = -(n.^2)*(pi.^2)*(t);
      e = exp(exponent);
      wave = sin(x.*n.*pi);
      u_trans = e.*wave*A(n);  %  u(x,t) term calculation
      u = u + u_trans;         %  u(x,t) summation
      n=n+1;
 end

%--Plot--
figure;
surfc(x,t,u)

title('Project 2')
xlabel('X')
ylabel('Time')

Any thoughts or insight would be really helpful!

Answer 1

[Image Analyst]

If you'd use the debugger you'd discover that you're trying to do an element-by-element multiplication of a 100x100 by a 1x100 by a 1x100. You can't do that. "e" is 100x100 - why is that? It comes down to t being 100x100. You need to look into what you're doing with meshgrid().

[Image Analyst]

http://blogs.mathworks.com/videos/2012/07/03/debugging-in-matlab/

Answer 2

[Mike]

Thanks, I used the debugger to find where my problem was. Now i am faced with a different problem. My plot comes out zeroed and i have no clue why. Any thoughts?

clc;
clear;

N=25;

% --Grid--
gridX = linspace(0,1,N);
gridT = linspace(0,0.5,N);
[x,t] = meshgrid(gridX,gridT);

A = linspace(0,1,N);
u = zeros(N,N);
xint = linspace(0,1,N);

%--Computation of An Terms--
n=1;
while n <= N;
    I(n) =  -(4*sin((pi*n)/2))/(pi*(n^2 - 4));
    A(n) = A(n) + I(n);
    n = n + 1;
end

while n <= N
    exponent = -(n.^2)*(pi.^2)*(t);  % n replaces lamda
    T = exp(exponent);
    X = A(n).*sin(n.*pi.*x);
    total = T*X;
    u(n) = u(n) + total;  %--Sum of all solutions--
    n = n + 1;
end

%--Plot--
figure;
surfc(x,t,u)

title('Project 2')
xlabel('X')
ylabel('Time')