Subs with 2 numbers returns a number

Subs when given 2 numbers, returns a number. But I need a string/function to be returned

example:

>> syms x y;
>> f=-y+x+2;
>> subs(f, [x,y], [2,2])
 
ans =
 
2
 
>> 

But I need it: -2+2+2

Answer 1

[Star Strider]

It is doing the substitution and the calculation at the same time, and providing the answer.

Using symbolic arguments instead —

syms x y a b 
f=-y+x+2;
subs(f, [x,y], [a,b])

ans = 

as expected.

.

Answer 2

[John D'Errico]

Simple enough. Convert the original expression to a string. Now just do string processing, with finds and replace operations.

Can you do it using symbolic computations? Probably not, since subs will combine those numeric constants for you automatically.