matlab二分法求方程x^3-x-1=0

matlab二分法求方程x^3-x-1=0

这是源代码:

在matlab中保存为:bisection.m

function

rtn=bisection(fx,xa,xb,n,delta)

%

Bisection

Method

%

The

first

parameter

fx

is

a

external

function

with

respect

to

viable

x.

%

xa

is

the

left

point

of

the

initial

interval

%

xb

is

the

right

point

of

the

initial

interval

%

n

is

the

number

of

iterations.

x=xa;fa=eval(fx);

x=xb;fb=eval(fx);

disp('

[

n

xa

xb

xc

fc

]');

for

i=1:n

xc=(xa+xb)/2;x=xc;fc=eval(fx);

X=[i,xa,xb,xc,fc];

disp(X),

if

fc*fa<0

xb=xc;

else

xa=xc;

end

if

(xb-xa)

end

>>f='x^3-x-1';

>>bisection(f,1,1.5,20,10^(-3))

[

n

xa

xb

xc

fc

]

1.0000

1.0000

1.5000

1.2500

-0.2969

2.0000

1.2500

1.5000

1.3750

0.2246

3.0000

1.2500

1.3750

1.3125

-0.0515

4.0000

1.3125

1.3750

1.3438

0.0826

5.0000

1.3125

1.3438

1.3281

0.0146

6.0000

1.3125

1.3281

1.3203

-0.0187

7.0000

1.3203

1.3281

1.3242

-0.0021

8.0000

1.3242

1.3281

1.3262

0.0062

9.0000

1.3242

1.3262

1.3252

0.0020

从结果可以看出,

这个解为:1.3262