Various functions depending on X

2022 11 18
1 个回答
更新时间：2022 11 18
3 次查看（30 天）

0 个投票

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))

请先登录，再回答此问题。

回答（1 个）

John D'Errico
John D'Errico 2022-11-18
Ran in:

0 个投票

Ran in:
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.

类别

在 帮助中心 和 File Exchange 中查找有关 Share and Distribute Software 的更多信息

标签

提问:

dylan
dylan
2022-11-18

回答：

John D'Errico
John D'Errico
2022-11-18

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by