信息与计算科学专业实习报告

信息与计算科学专业 专业实习报告

附录

function [x,fx,xflag]=find_roots1(f,c1,c2,rel_err) % f is the name of the function to be solved

% c1,c2 are the min and max bounds of x respectively % rel_err is the relative error,that is abs(f1n-f2n)/abs(f1-f2) % where f1n, f2n are the function values at the c1n and c2n % f1n, f2n are the function values at c1 and c2 % xflag is -1 if there's no root in range (c1,c2) % xflag equals to 1 if there is a root in range (c1,c2) % x is the root solved % fx is its value % example

% [x,fx,xflag]=find_roots1(@sin,0.1,pi+0.1,1e-6) %{ c1=0.01; c2=pi+0.1; rel_err=1e-3; f=@sin; %} xflag=-1; f1=feval_r(f,c1); f2=feval_r(f,c2); abs_f1_2=abs(f1-f2); if abs(f1) <= rel_err*abs_f1_2 x=c1; fx=f1; xflag=1; return;

elseif abs(f2) <= rel_err*abs_f1_2 x=c2; fx=f2; xflag=1; return;

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信息与计算科学专业 专业实习报告

elseif f1*f2 >0 x=nan; fx=nan; return; else for i1=1:100 c0=(c1+c2)/2; f0=feval_r(f,c0);

if abs(f0) <= rel_err*abs_f1_2 x=c0; fx=f0; xflag=1; return; elseif f1*f0 >0 c1=c0; f1=f0; else c2=c0; f2=f0; end

if abs(f1-f2)

elseif abs(f1-f2)>100*abs_f1_2 xflag=-1; x=nan; fx=nan; return; end end end

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