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Passing the numeric matrix to symbolic function

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Hello,
I have created a function containing symbolic expressions. The expressions make use of a symbolic matrix. I want to solve the function passing the numeric matrix which replaces the symbolic matrix and provides a numeric answer. I can't seem to understand how to pass the numeric matrix.
function example
R= sym('R',[3 3])
r_b= R([1 2], [3])
R_bar= R([1 2], [1 2])
R_til=R([2 3],[2 3])
syms alpha_bar beta_bar
a_bar= [1;alpha_bar]
b_bar= [beta_bar;1]
P= sym(R_bar*a_bar)
Q= sym(R_til*b_bar)
syms E_a E_b
u_bar= [1; 0]
v_bar= [0;1]
W = sym(E_a*u_bar)
X= sym(E_b*v_bar)
C= sym(P==W)
D= sym(Q==X)
[alpha_bar_, E_a_] = solve(P==W,[alpha_bar,E_a])
[beta_bar_, E_b_] = solve(Q==X,[beta_bar,E_b])
a_bar= [1;alpha_bar_]
b_bar=[beta_bar_;1]
delta= (a_bar)'*r_b
gamma_b = delta/E_b_
gamma_a= delta/E_a_
a= [a_bar;0]-(gamma_b*[0;b_bar])
b= [0;b_bar]-gamma_a*[a_bar;0]
end
My R is R= [1 1 0; 1 3 2; 0 2 3].
Any help on this example would be deeply appreciated.
Thank You.

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Accepted Answer

Karan Gill
Karan Gill on 14 Feb 2018
You're not passing any arguments to the function. To learn that, see function.
If you want a numerical result, instead of a symbolic solver like solve, use a numeric solver like vpasolve or fsolve.
Lastly, any numeric input can be converted to symbolic form by using sym(input).

  2 Comments

Vishakha Ramani
Vishakha Ramani on 14 Feb 2018
I read the link provided by you and converted numeric input to symbolic form. The solution worked. Thank you very much.

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More Answers (1)

Walter Roberson
Walter Roberson on 14 Feb 2018
subs(a, R, NumericR)
and you might want to double() the results.
You need to avoid assigning a numeric value to R itself for this to work.

  1 Comment

Vishakha Ramani
Vishakha Ramani on 14 Feb 2018
I wanted to pass the numeric matrix from the command window. I passed the appropriate arguments to the function and it worked. Thank you so very much for the help.

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