Is there any way to separate the terms of a product?

Question

Panagiotis Panagopoulos Papageorgiou 2019-2-17

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/445453-is-there-any-way-to-separate-the-terms-of-a-product

评论： Panagiotis Panagopoulos Papageorgiou 2019-2-19

采纳的回答： Walter Roberson

Hello,

Let's say I have this function_handle: f = @(x) exp(x-2)*log(x)

Is it possible to assign each function that comprises this product to its own seperate variable i.e:

g = exp()

h = x-2

j = log()

k = x

Thank you!

2 个评论
显示无隐藏无

John D'Errico 2019-2-17

编辑：John D'Errico 2019-2-17

在 MATLAB Online 中打开

Sure. Write your own expression parsing code.

f = @(x) exp(x-2)*log(x);
>> func2str(f)
ans =
    '@(x)exp(x-2)*log(x)'

Panagiotis Panagopoulos Papageorgiou 2019-2-18

Hello,

Seeing my question once more, I believe that I've not been specific enough.

In my programme I ask the user to enter his own function. Once that is done I'd like to "break" that function into seperate parts, and then assign each part to it's own variable. So if I input this:

exp(x-2)*log(x)

I want to get these variables:

g = exp(x)

h = x-2

j = log(x)

k = x

Thank you for your time and effort. :)

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Walter Roberson 2019-2-17

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/445453-is-there-any-way-to-separate-the-terms-of-a-product#answer_361466

在 MATLAB Online 中打开

If you have the Symbolic Toolbox, then

f = @(x) exp(x-2)*log(x)
syms x
temp = f(x);
op0 = feval(symengine, 'op', temp, 0)
rest = children(temp)
rest0 = arrayfun(@children, rest, 'uniform', 0)

and so on, taking op 0 and children each time. op 0 will be things like _mult and _plus for * and + (and subtraction -- subtraction is _plus of negative of the value).

With a little work, you could create a routine that broke expressions down into nested cell arrays or into nested struct.

This is not a nice interface, but it is all that is availabe in the symbolic toolbox in any released version.

3 个评论
显示 1更早的评论隐藏 1更早的评论

Walter Roberson 2019-2-18

symtree.m

I attached code that produces a nested cell parse tree. You could modify it.

The current last line has {op0} which will produce the token such as exp . You would want to look at length(rest) and use that many nominal variables similar to the representative_vars that I introduce near the beginning of the code to convert simple @functionname into functionname(x, y, z, ...) expressions.

Panagiotis Panagopoulos Papageorgiou 2019-2-19