How to get variable r recognised when inputting a matrice? eg matrix1 = [1, 0; 2/r, 1]

Get the message:

Unrecognised function or variable 'r'.

when trying to write the matrice:

matrix1 = [1, 0; 2/r, 1]

How do I get Matlab to recognise 2/r ?

I'm a nooby to Matlab, please be kind!

Answer 1

[Dyuman Joshi]

Use syms to make a symbolic variable (Note - It requires the symbolic math toolbox)

syms r
matrix1 = [1, 0; 2/r, 1]

matrix1 = 

Or if you are going to evaluate the value for some r, a better way would be to define a symbolic function

syms matrix1(r)
matrix1(r) = [1, 0; 2/r, 1]

matrix1(r) = 

matrix1(2)

ans = 

[Neil]

That's working now, thank you!

[Dyuman Joshi]

You are Welcome!

Answer 2

[Steven Lord]

Another approach, one that doesn't require Symbolic Math Toolbox, is to create a function that you can call with a specific value of r.

M = @(r) [1, 0; 2/r, 1]

M = function_handle with value:
    @(r)[1,0;2/r,1]

This is an anonymous function. To use this anonymous function, call it like you'd call any other function in MATLAB.

A = M(4)

A = 2×2

1.0000 0 0.5000 1.0000

B = M(2)

B = 2×2

1 0 1 1

C = M(1)

C = 2×2

1 0 2 1