How can I plot this code using the "plot" function?

x = [-1 0 1 2];
y = [1 2 -1 2];
P = cod_lagrange(x,y); %los coef aparecen de la forma Ax^n + Bx^n-1 + ... + D
pretty(poly2sym(P))
%polyval(P,1.5) %para evaluar el polinomio en un punto (1.5 en este caso)
SP = poly2sym(P); %Guardo en SP el polinomio
figure
ezplot(SP,[-1.0 2.0])
fplot(SP,[-1.0 2.0])

if I do

z = 1: .5: 2
plot (z, SP)

gives error because SP is type "sym" Matlab says: "Error using plot Data must be numeric, datetime, duration or an array convertible to double."

Answer 1

[Walter Roberson]

The solution is explained at https://www.mathworks.com/matlabcentral/answers/358876-solve-and-plot-symbolic-equation#answer_283557