Accessing a matrix in Matlab - user-interface

Question

Assume user input data as below. I define my matrix is cost. The matrix i created is 3 by 3 matrix. So the matrix should form like this:
cost = [c11 c12 c13
c21 c22 c23
c31 c32 c33]
Since i want to display set of row, i do it like this :
c1 = cost(1,:); % it will become c1 = c11 c12 c13
c2 = cost(2,:); % it will become c2 = c21 c22 c23
c3 = cost(3,:); % it will become c3 = c31 c32 c33
Then i want the value in the matrix. I do it like this.
c11 = cost(1,1);
c12 = cost(1,2);
c13 = cost(1,3);
c21 = cost(2,1);
c22 = cost(2,2);
c23 = cost(2,3);
c31 = cost(3,1);
c32 = cost(3,2);
c33 = cost(3,3);
So this is the equation that i want to use for this type of matrix.
lambda =
((8*c13*c23*c33*Pdt)+(4*c12*c23*c33)+(4*c13*c22*c33)+(4*c13*c23*c32)) ./ (4*c23*c33)+(4*c13*c33)+(4*c13*c23));
So my problem is, if i want to make 4 by 3 matrix, and it would generate a matrix like this:
cost = [c11 c12 c13
c21 c22 c23
c31 c32 c33
c41 c42 c43]
The equation that i want to use for this matrix(4 by 3) is quite different. So how im gonna do it? Do i need to use if else statement? or do while? Can anyone help me solve this? Can anyone create the code?

Answer 1

Why do you explicitly create the variables c11, c12, ...? Surely it would be easier to just access the matrix in your equation like this:
lambda =
((8*cost(1,3)*cost(2,3)*cost(3,3)*Pdt)+(4*cost(1,2)*cost(2,3)*cost(3,3)+(4*cost(1,3)*cost(2,2)*c(3,3))+(4*cost(1,3)*cost(2,3)*cost(3,2)) ./
(4*cost(2,3)*cost(3,3))+(4*cost(1,3)*cost(3,3))+(4*cost(1,3)*cost(2,3)));
For your question, yes, just use a simple if statment, like this:
if size(cost,1) == 3
%equation for matrix size 3x3
else
%equation for matriz size 4x3