I need help with this false position script

Question

AJ516 2019-10-18

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/486028-i-need-help-with-this-false-position-script

编辑： Stephan 2019-10-19

I'm not sure where the issue is. Note the percent notes below the script has some commands that need to copy and pasted into the command box.

function root= fp(func,xl,xu,es,max)

if func(xl)*func(xu)>0

error('input error')

end

if nargin<5

max=50;

end

if nargin<4

es=0.001;

end

iter=0;

xr=xl;

while(1)

xrold=xr;

xr=xu-func(xu)*(xl-xu)/(func(xl)-func(xu));

iter=iter+1;

if xr~=0

ea=abs((xr-xrold)/xr)*100;

end

test=func(xl)*func(xr);

if test<0

xu=xr;

elseif test>0

xl=xr;

else

ea=0;

end

if ea<=es||iter>=max

break

end

root=xr;

%Type the following commands below

%format long

%fx=@(x)-12-(21*x)+(18*x^2)-(2.75*x^3)

%fp(fx,-1,0,0.001)

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Answer 1

Stephan 2019-10-19

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/486028-i-need-help-with-this-false-position-script#answer_397214

编辑：Stephan 2019-10-19

No idea what your problem is, code runs for me:

format long
fx=@(x)-12-(21*x)+(18*x^2)-(2.75*x^3)
a =sprintf('%.8f', fp(fx,-1,0,0.001))
function root= fp(func,xl,xu,es,max)
if func(xl)*func(xu)>0
  error('input error')
end
if nargin<5
  max=50;
end
if nargin<4
  es=0.001;
end
iter=0;
xr=xl;
while(1)
  xrold=xr;
  xr=xu-func(xu)*(xl-xu)/(func(xl)-func(xu));
  iter=iter+1;
    if xr~=0
    ea=abs((xr-xrold)/xr)*100;
    end
    test=func(xl)*func(xr);
    if test<0
        xu=xr;
    elseif test>0
        xl=xr;
    else
        ea=0;
        end
    if  ea<=es||iter>=max
        break
    end
    end
root=xr;
end