Writing a funciton for e^x values?

I am not sure what is wrong with my code, here is the prompt:

Write a function called e_to_the_x to estimate using its Taylor series:

starting with n =0, add terms until 2 subsequent approximations differ by less than using a while loop. (HINT: use the built-in function factorial()).

I am getting values but when I call e_to_the_x(-1) and e_to_the_x(1) it says I have incorrect values. Here is my code:

function [y1,y2] = e_to_the_x(x)
n=0
y1=(x^n)/factorial(n)
y2=y1+(x^n)/factorial(n)

while abs(y2-y1)>1e-6
    y1=y2
    y2=y1+(x^n)/factorial(n)
    n=n+1
end
end 

Answer 1

[David Hill]

function [y1,y2] = e_to_the_x(x)
n=0;
y1=(x^n)/factorial(n);
n=n+1;
y2=y1+(x^n)/factorial(n);
n=n+1;
while abs(y2-y1)>1e-6
    y1=y2;
    y2=y1+(x^n)/factorial(n);
    n=n+1;
end
end 

You forgot to advance n.

Answer 2

[James Tursa]

You use the same n value for the first three terms. You need to increment n each time you add a term, including the first two terms that are outside of the while loop.