Various functions depending on X

I wanted to create a function that consists of a number and functions and works like this

if x<-1 y=-x^2-4*x-2

if |x|<1 y=|x|

if x>1 y=2-e^(sqrt(x-1))

Answer 1

[John D'Errico]

If the function is symbolic, then use piecewise.

help piecewise

--- help for sym/piecewise ---

 PIECEWISE Conditionally defined symbolic object
    PW = PIECEWISE(CONDITION1, VAL1, CONDITION2, VAL2, ..., <OTHERWISEVAL>)
 
    Create a conditionally defined symbolic object. It equals the k-th
    value if the k-th condition holds and the first k-1 conditions are
    false. If all conditions are false, it equals otherwiseVal.
    The final argument otherwiseVal may be omitted; it defaults to sym(NaN).
    In contrast to an if statement, the truth value of the conditions need
    not be decidable at the time the conditional object is defined.
 
    Example:
       syms x
       pw = piecewise(x<0, -1, x>=0 & x<2, 2)
       subs(pw, x, -2)
       subs(pw, x, 1)
       subs(pw, x, 3)
 
       syms x
       pw = piecewise(x<0, 0, x)
       subs(pw, x, -2)
       subs(pw, x, 1i)
 
       syms pw(x) y
       pw(x) = piecewise(x>0, 1, x < 0, -1, 0)
       pw(-5)
       pw(0)
       assume(y>2)
       pw(y)
 
    See also IF, SYM/ASSUME, SYM/ASSUMEALSO.

    Documentation for sym/piecewise
       doc sym/piecewise

Note that your function lacks definition, since you do not say what happens when x==1 or x==-1.

For a general matlab function, you can use my piecewise_eval, it is on the file exchange.

https://www.mathworks.com/matlabcentral/fileexchange/9394-piecewise-functions?s_tid=srchtitle

Pretty old now, but it should still work.

I also see many other tools on the FEX that claim to do the job too.