Error using symfun/subsref (line 203) Invalid argument at position 2.

I want to create a "for" that iterates 3 times with a symbolic function and then organize a matrix whit this 3 functions. When i try to array N, i don't know how to call the positions from the cicle "for", so I'm geting the error "Error using symfun/subsref (line 203) Invalid argument at position 2. Symbolic function expected 2 input arguments but received 1", because it is reading the numbers in N(1), N(2) and N(3) as variables.

syms x y
nnodos = 3 ; 

A = 9.5 

A = 9.5000

a = [16
    4.5
    -11];

b = [-2
    3
    -1];

c = [-1.5
    -2.;5
    -4];

for i= 1:nnodos
N = symfun(((1/(2*A))*(a(i)+b(i)*x+c(i)*y)),[x y]);
end

N = [0 N(1) 0 N(2) 0 N(3) 0; 0 N(1) 0 N(2) 0 N(3)];

Answer 1

[Torsten]

N(i) = symfun(((1/(2*A))*(a(i)+b(i)*x+c(i)*y)),[x y]);

instead of

N = symfun(((1/(2*A))*(a(i)+b(i)*x+c(i)*y)),[x y]);

And

N = [0 N(1) 0 N(2) 0 N(3) 0; 0 N(1) 0 N(2) 0 N(3) 0];

instead of

N = [0 N(1) 0 N(2) 0 N(3) 0; 0 N(1) 0 N(2) 0 N(3)];

Answer 2

[Paul]

Hi Catalina,

Need to subscript N in the foor loop to create a vector with 3 elements. Also, the final construction of N had an error, corrected below. Also, I think there was a typo in c, also corrected below

syms x y
nnodos = 3 ; 
A = 9.5 

A = 9.5000

a = [16
    4.5
    -11];
b = [-2
    3
    -1];
% was
% c = [-1.5
%     -2.;5
%     -4];
c = [-1.5
    -2.5
    -4];

for i= 1:nnodos
N(i) = symfun(((1/(2*A))*(a(i)+b(i)*x+c(i)*y)),[x y]);
end
N

N = 

% added an additional zero at the end of the second row so it has the same
% number of elements as the first row
N = [0 N(1) 0 N(2) 0 N(3) 0; 0 N(1) 0 N(2) 0 N(3) 0]

N = 

The for loop can be avoided, and there does not appear to be a reason to construct each element of N as a symfun becasue the final form of N is just an exression.

N =1/(2*A)*(a+b*x+c*y);
N = [0 N(1) 0 N(2) 0 N(3) 0; 0 N(1) 0 N(2) 0 N(3) 0]

N =