Is there a function or technique for converting MATLAB's symbolic expressions to expressions that can be evaluated element-wise?
As an example, the command
a = solve('x^2 + a*x + b == 0')
gives the output
a =
(a^2 - 4*b)^(1/2)/2 - a/2
- a/2 - (a^2 - 4*b)^(1/2)/2
The desired output, however, which allows a and b to be arrays, is
a =
(a.^2 - 4*b).^(1/2)/2 - a/2
- a/2 - (a.^2 - 4*b).^(1/2)/2
solve('x^2 + a*x + b == 0') returns a 2x1 sym. I understand you want to evaluate the solution for various a and b values. To do this, you first need to convert your sym to a function using matlabFunction.
s = solve('x^2 + a*x + b == 0');
f = matlabFunction(s);
Now f is a function of two input arguments a and b. Try it on two vectors of three a and b values:
f([1 2 3],[1 1 1])
and you will get a 2x3 array of the solutions.
You can also use subs to achieve what you want to do:
subs(s,{'a' 'b'},{[1 2 3 ] [1 1 1]})
will substitute [1 2 3] for a and [1 1 1 ] for b and return a 2x3 sym. If you want to evaluate it, just use eval:
eval(subs(s,{'a' 'b'},{[1 2 3 ] [1 1 1]}))