Introduction to MATLAB - Numerical Methods in Engineering with MATLAB - page 18

end
error('Too many iterations')

>>x=solve(2) %numIternotprinted

x=

1.8955

>> [x,numIter] = solve(2) % numIter is printed
x=

1.8955
numIter =
4

>> format long
>>x=solve(2,1.0e-12) %Solvingwithextraprecision

x=
1.89549426703398

>>

Evaluating Functions

Let usconsideraslightlydifferent version of the function solve shown below. The
expression for dx , namely f ( x ), is now codedinthe function myfunc ,

so that solve contains a call to myfunc . This will work fine, provided that myfunc is
stored under the file name myfunc.m so thatMATLAB can find it.

=− /

x f ( x )

function [x,numIter] = solve(x,epsilon)
if nargin == 1; epsilon = 1.0e-6; end
for numIter = 1:30
dx = myfunc(x);
x=x+dx;
if abs(dx) < epsilon; return; end

end
error('Too many iterations')

functiony=myfunc(x)
y = -(sin(x) - 0.5*x)/(cos(x) - 0.5);

>>x=solve(2)
x=

1.8955