Extracting numeric values from symbolic variables

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.

Answer 1

[Thiago Henrique Gomes Lobato]

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

[madhan ravi]

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

[Thiago Henrique Gomes Lobato]

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

Answer 2

[Alphonce Owayo]

For example;

syms x y

eqn1=x+y==20;

eqn2=2.3x-9y==13;

soln=vpasolve(eqn1,eqn2);

xsoln=soln.x;

ysoln=soln.y;

or

xsoln=double(soln.x);

ysoln=double(son.y);

disp(xsoln);

disp(ysoln);

Answer 3

[madhan ravi]

== forms an equation , it DOESN’T assign any values.

[madhan ravi]

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

I would suggest you to do the below instead:

 c = num2cell(x);
 celldisp(c)

Answer 4

[Alphonce Owayo]

shown above is how to extract numeric values from symbolic variables and display them in the command window.