Error R_tilde = builtin('s​ubsref',L_​tilde,Idx)​;

clc;
clear all

syms x y F(y)
f(y)=(10./3).*((x).*(y.^(2./5)));
eqn=diff(F(y))==f(y);
cond = [y(0) == 4];

Array indices must be positive integers or logical values.

Error in indexing (line 1075)
R_tilde = builtin('subsref',L_tilde,Idx);

sol=vpa (dsolve(eqn,cond))

I am Receving these errors.

Subscript indices must either be real positive integers or logicals.

R_tilde = builtin('subsref',L_tilde,Idx);

cond = [y(0) == 4];

Answer 1

[Cris LaPierre]

The error is because y is a variable, not a function, so y(0) is being treated as an indexing operation. Since MATLAB uses 1-based indexing, it is returning an error. Perhaps you meant to write f(0) in your condition statement?

y=1:3;
% works
y(2)

ans = 2

% your error
y(0)

Array indices must be positive integers or logical values.