Plot integral with fplot

8 次查看（过去 30 天）
Federico Spada
Federico Spada 2019-2-25
评论： Star Strider 2019-2-25
Hi,
I have this code:
string='int(x^2,x)';
y=str2func(['@(x)' string]);
Then I try to plot it with fplot
fplot(y)
But the problem is that axes remain white, without an error or anything else.
I've already solved the problem with symbolic toolbox
syms y(x)
y(x)=eval(string)
fplot(y)
But this solution is terribly slow and for the application that I'm developping it is important a solution as fast as possibile. If I use str2func with functions that require only one input (cos,sin,...) it works perfectly but with function with 2 or more input axes remain white. Have you a solution to suggest me? Thanks in advance.

请先登录，再回答此问题。

采纳的回答

Star Strider
Star Strider 2019-2-25
Using str2func is not the correct approach for dealing with symbolic expressions, and especially those that involve symbolic functions (such as int) that only operate in the symbolic context.
Try this instead:
string = 'int(x^2,x)';
y = matlabFunction(str2sym(string))
fplot(y)
That is still significantly inefficient, however it has the one redeeming feature of producing the result you apparently want, using the character vector you began with.
  4 个评论
显示 2更早的评论
Federico Spada
Federico Spada 2019-2-25
Ok, perfect! Thank you!
Star Strider
Star Strider 2019-2-25
As always, my pleasure!

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 Calculus 的更多信息

标签

产品


版本

R2018b

Community Treasure Hunt

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

Start Hunting!

Translated by