defining symbolic piecewise function

18 次查看（过去 30 天）
Francesco Collini
Francesco Collini 2017-12-20
回答： Francesco Collini 2019-2-28
Good evening, I have an issue trying to define a piecewise symbolic function in matlab.
I already tried using the piecewise predefined function as shown in the next piece of code:
a = sym('a'); l = sym('l');
r_i = symfun(r_c(a) + r_1, a); l_i = symfun((pi/2)*r_c(a), a); l_2 = symfun(l_i(a) + r_2 - r_i(a), a);
r = symfun(piecewise((0 <= l) && (l < l_i(a)),...
r_1 + r_c(a) * (1 - cos(l / r_c(a))),...
(l_i(a)<=l) && (l<l_2(a)),...
r_i(a) + l - (pi/2) * r_c(a)),...
[l, a]);
but it shows this error "Conversion to logical from sym is not possible.".
I guess it is because I can not use a symbolic function in the chain of inequalities, but I do not know how to fix this, so please could anyone help me? Thankyou very much and merry Christmas!!
PS
This piece of code is contained in a function.m file.

请先登录，再回答此问题。

采纳的回答

Francesco Collini
Francesco Collini 2019-2-28
I found out that the solution for this problem is:
a = sym('a'); l = sym('l');
r_i = symfun(r_c(a) + r_1, a); l_i = symfun((pi/2)*r_c(a), a); l_2 = symfun(l_i(a) + r_2 - r_i(a), a);
r = symfun(piecewise((0 <= l) & (l < l_i(a)),...
r_1 + r_c(a) * (1 - cos(l / r_c(a))),...
(l_i(a)<=l) & (l<l_2(a)),...
r_i(a) + l - (pi/2) * r_c(a)),...
[l, a]);
The problem was in the definition of the intervals, where a single character "&" must be used instead two "&&" to define an interval under more than one condition.

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Assumptions 的更多信息

标签

产品

Community Treasure Hunt

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

Start Hunting!

Translated by