How to use str2func with a function handle in the string

9 次查看（过去 30 天）
dario
dario 2020-5-29
评论： dario 2020-5-29
Hi,
I want to insert a function handle in the input string of str2func but I get an error.
string1 = '@(x)sin(x)';
A = str2func(string1);
string2 = '@(x,y)(A(x) + sin(y))'
B = str2func(string2);
B(pi/2,pi/2)
It says: Undefined function or variable 'A'.
How can I fix it?
Thanks

请先登录，再回答此问题。

采纳的回答

Tommy
Tommy 2020-5-29
From the documentation for str2func,
"Workspace variables are not available to the str2func function."
See this answer. You could do something like this:
string1 = '@(x)sin(x)';
A = str2func(string1);
string2 = ['@(y)(' num2str(feval(A,pi/2)) ' + sin(y))'];
B = str2func(string2);
B(pi/2)
  6 个评论
显示 4更早的评论
Tommy
Tommy 2020-5-29
Gotcha. There's always eval...
string1 = '@(x)sin(x)';
A = str2func(string1);
string2 = '@(x,y)(A(x) + sin(y))';
B = eval(string2);
B(pi/2,pi/2)
I guess I ignore eval by default, but it definitely works here. I would still recommend either of the previous answers.
Or here's a somewhat interesting possibility:
string1 = '@(x)sin(x)';
A = str2func(string1);
string2 = @(x) (['@(y)(' num2str(feval(A,x)) ' + sin(y))']);
B = @(x,y) feval(str2func(string2(x)), y);
B(pi/2, pi/2)
Maybe it can be simplified.
Good idea, I'm curious!

请先登录，再进行评论。

更多回答（0 个）

类别

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

标签

产品


版本

R2019a

Community Treasure Hunt

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

Start Hunting!

Translated by