# How can I define the error function and use a Maclaurin series to approximate a value?

11 views (last 30 days)
codeconstructo on 3 Mar 2023
Commented: Sam Chak on 3 Mar 2023
My question is: erf (x) = 2/sqrt(pi)*integral(exp(-(t^2)) from 0 to x
(a) Use the Maclaurin series (Taylor series centered at 0) to construct a table for erf (x) that is accurate
to 10^-4 for erf (xi) where xi = 0:2i for i = 0; 1; : : : ; 5.
I first defined the function and then realized that erf is a built in function so I tried
erf = @(x) erf(x)
erf = function_handle with value:
@(x)erf(x)
but got this response:
Unable to find function@(x)(2/(sqrt(pi)))*integral(exp(-(t^2)),0,x) within
C:\Users\dboeh\OneDrive\Documents\NAU\MAT 362\dbb223_03.m.
Does anyone have ideas?

Sam Chak on 3 Mar 2023
Are you looking for something like this?
syms x
T1 = taylor(erf(x))
T1 = Sam Chak on 3 Mar 2023
The built-in erf() function is stored in MATLAB installation directory.
which erf
built-in (/MATLAB/toolbox/matlab/specfun/@double/erf) % double method
You created an anonymous function in a m-file script (dbb223_03.m) which has the same filename as the built-in one and ran the m-file in OneDrive. So, it tries to search erf within the m-file. Try assigning another name.
% Creating an anonymous function
anonfcn = @(x) erf(x)
anonfcn = function_handle with value:
@(x)erf(x)
% Built-in
erf(pi)
ans = 1.0000
% Test
anonfcn(pi)
ans = 1.0000