Creating a Nested Function

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Kelly
Kelly 2013-3-29
I am trying to create a nested function, but I get an error saying that the variable that I've chosen is already being used even though that's the variable that I need as an input for my second function to compute the equation.
function [root,numit,err] = newton(x,tol,fx,ddx)
err = abs(fx(x));
numit = 0;
while(err > tol && numit < 1000);
numit = numit + 1;
x = x - fx(x)/ddx(x);
err = abs(fx(x));
end
if (numit == 1000)
disp('Maxed out on iterations.')
err;
end
root = x;
function root = x
dx = 0.001;
for i = 2:length(x)-1;
fx = exp(cos(x) + sin(x)) - 2;
dxf=(diff(2:i)-diff(1:(i-1)))/2*dx';
end
root = dxf(x);
end
end
root is my desired output and it is denoted by x. I keep getting an error about x being used as a variable and in the nested function in the same scope. What am I doing wrong?

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回答（1 个）

Azzi Abdelmalek
Azzi Abdelmalek 2013-3-29
编辑：Azzi Abdelmalek 2013-3-29
Change the name of your nested function, because you are using x as function name and variable
function root = new_name(x)
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Kelly
Kelly 2013-3-29
编辑：Azzi Abdelmalek 2013-3-29
Ok, I got all the computations to work correctly. Now I'm stuck on plotting. I'm creating a 1x2 and the first plot is just the exact derivative of the function and the second should be the numerical approximation.
clc; clear all; close all;
% Equation 1
tol = 0.001; % for central difference dx == tol
ns = 5;
a = 0;
b = 7;
fx = inline('exp(cos(x) + sin(x)) - 2');
ddx = inline('(exp(cos(x) + sin(x)))*(cos(x)-sin(x))');
% Incremental Search Method
[nroots,low,high] = increm_mod(fx,a,b,ns,tol);
for j = 1:length(low)
fprintf('\n')
disp(['The First Equation has ',num2str(nroots),' roots.'])
fprintf('\n')
fprintf('-----------------------------------------------------------------')
fprintf('\n')
disp('USING THE NEWTON-RAPHSON METHOD:')
fprintf('\n')
% Newton Estimate
guess = 2*(a + b)/3;
[root_n(j),numit_n,err_n(j)] = newton(low(j),tol,fx,ddx);
disp(['Root # ',num2str(j),' = ',num2str(root_n(j))])
disp(['Error # ',num2str(j),' = ',num2str(err_n(j))])
disp(['Number of Iterations # ',num2str(j),' = ',num2str(numit_n)])
fprintf('\n')
end
n = 0;
ns = 100;
dx = (b-a)/ns;
for j = a:dx:b
n = n+1;
f_p(n) = fx(j);
x_p(n) = j;
end
figure(1)
subplot(2,1,1)
plot(x_p,f_p);
hold on
grid on
plot(fx,dx,'ko')%%%%%%%%here's is my problem
xlabel('x-values')
ylabel('fx')
title('Solution Using Newton-Raphson')
subplot(2,1,2)
plot(root_n,root_err,'ko')
xlabel('x values')
ylabel('my function')
I'm not sure if I'm plotting the right variables for the derivative because my function and derivative are inline functions.
Azzi Abdelmalek
Azzi Abdelmalek 2013-3-29
If the answer helped, accept the answer and post a new question.

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