How to set a function that can return different value for different range in MatLab? - piecewise -- MatLab

[Ans]

piecewise command

I think explanations of matlab help doc are

I think I can not use greater way to describe

--- 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.

pw = piecewise(cond1,val1,cond2,val2,...,<otherwiseVal>)

Type of <otherval> must be constant.

If <otherVal> was not given, it is NaN by default.

more details on:

I think the example from matlab help doc is great, so I uses these examples.

clear

clc

       syms x

       pw = piecewise(x<0, -1, x>=0 & x<2, 2)

       subs(pw, x, -2) %-1

       subs(pw, x, 1)  %2

       subs(pw, x, 3)  %NaN

       % this cause compiler error.

       %pw(7)

       syms x

       pw = piecewise(x<0, 0, x)

       subs(pw, x, -2) %0

       %same as subs(pw,x,real(1i))

       subs(pw, x, 1i) %1i

       %pw(x) is a function

       syms pw(x) y

       pw(x) = piecewise(x>0, 1, x < 0, -1, 0)

       pw(-5)%-1

       pw(0)%0

       assume(y>2)

       pw(y)%1