Extracting numeric values from symbolic variables

Question

ali akbar 2020-9-6

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/589657-extracting-numeric-values-from-symbolic-variables

回答： Alphonce Owayo 2021-2-23

I have two matrices say

x=[2 4 9 10];
syms c [1 4];
x==c
it returns
2=c1
4=c2
9=c3
10=c4

However when I write c1 in command window, it returns symbolic 'c1'.

I wanted to extract these numeric values or assign these values to c vector. How one would go around this.

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Answer 1

Thiago Henrique Gomes Lobato 2020-9-6

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/589657-extracting-numeric-values-from-symbolic-variables#answer_490564

编辑：Thiago Henrique Gomes Lobato 2020-9-6

在 MATLAB Online 中打开

x==c

The "==" operator is normally used as a logic comparison operation, not an assignment. In the case of using symbolic variables, "==" defines an equation, which could be solved, for example, with the matlab function solve. If you want to give values to your variables, use only one "=" sign, for example:

x=[2 4 9 10];
syms c [1 4];
>> c(1) = 2
 
c =
 
[ 2, c2, c3, c4]
 
>> c=x
c =
     2     4     9    10

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madhan ravi 2020-9-6

“ is a logic operation”. Not in this case when it contains a symbolic variables it forms an equation.

Thiago Henrique Gomes Lobato 2020-9-6

You're right, it becomes an equation when it contain symbolic variables. Since I believe he was knew to matlab I thought the more general definition of the operator would be easier to understand/apply to future cases. I will edit the answer accordingly

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