Error evaluating symbolic expressions with symbolic arrays.

I get an error when I run this code (R2017a):

x = sym('x',[1 3]);
y = x(1) + x(2) + x(3);

x(1)=1;
x(2)=1;
x(3)=1;

double(subs(y))

If instead of an array of syms I use separate syms variables, the code runs with no errors. This is the error I get:

Error using symengine
DOUBLE cannot convert the input expression into a double array.

Error in sym/double (line 643)
        Xstr = mupadmex('symobj::double', S.s, 0);

How can I fix this mantaining the array of syms? It would be great to keep the array as I need to use large arrays of syms.

Answer 1

[Walter Roberson]

x(1)=1; does not set x1 to 1: it changes the vector x to [1, x2, x3]

Instead,

X = [1, 1, 1];
subs(y, x, X)