manipulation of non numerical matricies

I am trying to calculate the answer to 4 simulataneous equations throught the use of matrices. For this I have the following arrangement:

Ax= y

A=[1 1 1 0
0 (d-f) -f 1
0 0 (1/6)*d^3 (-1/2)*d^2
0 (1/6)*(f-d)^3 (1/6)*f^3 -(1/2)*f^2]

x=[r1
r2
r3
m3]

y= [1 1 1 1 
-(f-a) -(f-b) -(f-c) -(f-e)
(1/6)*(d-a)^3 (1/6)*(d-b)^3 (1/6)*(d-c)^3 0
(1/6)*(f-a)^3 (1/6)*(f-b)^3 (1/6)*(f-c)^3 (1/6)*(f-e)^3]

how do i get matlab to deal with no numeric inputs in a matrix? currently i would have to assign a value to each of the lower case constants for it to calculate.

thanks in advance.

[Fangjun Jiang]

You can use {}Code format next time.

[Matthew]

could you explain further? what is {} code?

thanks

[Fangjun Jiang]

After you post the question, you probably see the format is different. There are quite a few formatting buttons above the question box. You can edit your question too, use those formatting buttons.

[Fangjun Jiang]

http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

Answer 1

[Fangjun Jiang]

You are right. If you specify the value of those variables such as d,f,r1,r2,r3,m3,a,b,c,e etc. ahead of the matrix A and y, everything should work out, which means you'll have the correct value for A and y.

What is x? If everything is known, what equation are you trying to solve?

[Matthew]

x is one of 3 reaction forces and one moment for a beam with three constraints and four loads.

i do not want to find the exact values, instead i want to create a equation for each 'x', i.e. r1,r2,r3.... in terms of a,b,c etc.

[Fangjun Jiang]

For that, you need the Symbolic Math Toolbox. Most of the MATLAB products deal with only numerics.

http://www.mathworks.com/products/symbolic/?s_cid=global_nav