How to convert symbolic calculation to numeric?

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Hi, I want to convert symbolic calculations into numeric one and substitute in the MATLAB program. This is because symbolic computation is taking a lot of time to do. Is there any way to convert symbolic calculation into numeric? Also I have one more question. I defined a function
f=sym('x1^2+2*x2^2+2*x3^2+2*x1*x2+2*x2*x3')
p=[1,1,1];
t2=p(1);
t2=evalAt(f,[x1=p(1),x2=p(2),x(3)=p(3),a=b]);
MATLAB gives error. I really don't understand what is problem. We do such substitutions in other matrices a=p(1) and so on. Why is this error? Really hard time for me. People, please help.

Answers (1)

Walter Roberson
Walter Roberson on 22 Oct 2013
Where did you do the
syms x1 x2 x(3) a
Also note that your expression uses x3 but your evalAt uses x(3)
  4 Comments
Amit Kumar
Amit Kumar on 22 Oct 2013
A Jenkins: My mistake, I did define b but forgot to put in this code. Thanks for this!
Walter Roberson: Thank you very much providing some solution. I was trying really hard to get this. Thanks!

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