Error: In an assignment A(I) = B, the number of elements in B and I must be the same.

The main code below for function Vt creates a 241 x 1 matrix. I want to repeat the calculations and store it in a new matrix that is 241 x 10, so each column has a new set of data repeated.

When I try this as shown below i get the error message? How do i change it to get a 241 x 10 matrix.

     for j=1:10
    Vt(j) = V*exp((r-(sigma^2)/2)*(0:1:N)'/N*T+ sigma*([0; cumsum(randn(N,1))]/sqrt(N))*sqrt(T));
    end
     Error: In an assignment  A(I) = B, the number of elements in B and I must be
    the same.

 function Firmvalue = GBM_FV(V,K,T,r,sigma)
  %T = 20; % Time until maturity
  %r = 0.05; % The risk free interest rate
  %sigma = 0.20; % The asset volatility
  %V = 100; % Starting asset value
  %K = 75; % The principal of the debt

N = 240;
Vt = V*exp((r-(sigma^2)/2)*(0:1:N)'/N*T+ sigma*([0; cumsum(randn(N,1))]/sqrt(N))*sqrt(T));

[Jan]

Because we neither know the size of "sigma", "r" and "T", nor the value of "N", we cannot run your program. In addition it is not clear, which variable you want to be a [241x10] array. It would be helpful, if you mention, which line causes the error.

[Sap]

sigma, r and T are all scalars and mentioned above. N=240.

I wanted Vt to be the 241 * 10 matrix. I don't mind giving the matrix a different name either.

[Sap]

The error appears after the following line:

for j=1:10

Vt(j) = V*exp((r-(sigma^2)/2)*(0:1:N)'/N*T+ sigma*([0; cumsum(randn(N,1))]/sqrt(N))*sqrt(T));

end

Answer 1

[Walter Roberson]

It appears to me that inside the exp() you are adding two column vectors of length N+1 each. That part should work fine, and exp() of that should give you a column vector of length N+1

Now you have V*exp(....) and "*" is the matrix multiplication operation. What size is V? We don't know, but the comment suggests that it is a scalar. If so then the result of the matrix multiplication would be a column vector of length N+1. And you then try to store those N+1 elements into a single numeric array location, Vt(j)

Perhaps what you want is to assign to Vt(:,j)

[Sap]

Thank you very much, it worked! :)