index notation symbolic toolbox

2013 11 4
6 个回答
更新时间：2020 2 26
3 次查看（30 天）

1 个投票

example: fi = sym('fi',[1 2]) fi =
[ fi1, fi2]
I want this to be: fi =
[ fi(1), fi(2)]
This in order to use outcome of symbolic manipulation directly in my matlab code.

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Dinant
Dinant 2014-2-19
Really? Somebody of the Mathworks?
Sean de Wolski
Sean de Wolski 2014-2-20
Dinant, I answered your question and provided you with code that does exactly what you asked for. If it's not, please clarify in your comments what you actually want.
Dinant Kistemaker
Dinant Kistemaker 2019-2-19
Thanks for the help, but you did not. I have reinitiated my post in hope I can get a workaround for this...

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回答（6 个）

Dinant
Dinant 2013-11-4

0 个投票

hmmm, what do you mean with the question mark?

7 个评论
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Sean de Wolski
Sean de Wolski 2013-11-4
Is this what you're looking for?
Dinant
Dinant 2013-11-4
that gives: fi =
[ 1, 2]
so no.
Sean de Wolski
Sean de Wolski 2013-11-4
Which can then be indexed like this:
fi(1)
fi(2)
Which is what you asked for.
Dinant
Dinant 2013-11-4
No it is not. your suggestion simply outputs 1 if i type fi(1). I know I can index it, but, as mentioned in the original posting, I want the output indexed.
if I type fi, I want the answer to be: fi = [ fi(1), fi(2)], or if I type sin(fi(1) I want the output to be sin(fi(1)) and not sin(fi1).
Sean de Wolski
Sean de Wolski 2013-11-4
Dinant, this is what my code does:
clear fi;
fi = sym([1 2]);
sin(fi(1))
It will not return two separate outputs because this is not how MATLAB works. Consider the same question for doubles:
[D(1) D(2)] = [1 2]; %error!
You would need to do this on two lines:
D(1) = 1;
D(2) = 2;
Knowing [1 2] upfront you would want
D = [1 2]
Then
D(1)
Dinant
Dinant 2013-11-4
I appreciate your help.
My question relates to the fact that directly want to use the output of symbolic manipulations in my matlab code that is vectorized. Symbolic output is not. It makes from fi(1) fi1. I do not want that. I want the output to be in terms of fi(1), fi(2), etc.
Sean de Wolski
Sean de Wolski 2013-11-4
What release are you using? Because on mine(R2013b) it creates a 1x2 sym
Code:
fi = sym([1 2])
size(fi)
sin(fi(1))
Printed:
fi =
[ 1, 2]
ans =
1 2
ans =
sin(1)

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Dinant Kistemaker
Dinant Kistemaker 2019-2-19

0 个投票

I am still very much looking forward to an answer to my question. It is really annyoing that the printed format is not in vector notation. I want to use the output for some symbolic manipulations in my code and I want to use vector notation.
if I type:
fi = sym ('fi',[1 3]);
x=cos(fi)
>>x =
[ cos(fi1), cos(fi2), cos(fi3)]
I would very much want to have the answer in vector notation like:
x =
[ cos(fi(1)), cos(fi(2)), cos(fi(3))]
Dinant Kistemaker
Dinant Kistemaker 2020-2-26

0 个投票

I am so looking forward to an answer to my problem...
Somebody from the Mathworks?

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Steven Lord
Steven Lord 2020-2-26
If you want an official MathWorks answer please contact Technical Support directly using the telephone icon in the upper-right corner of this page.
I suspect you will not be able to do what you want with sym or syms. Depending on what "use outcome of symbolic manipulation directly in my matlab[sic] code" means the matlabFunction function may be of use.

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Dinant
Dinant
2013-11-4

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Steven Lord
Steven Lord
2020-2-26

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