資源簡介
基于龍貝格算法的積分,可計算一維和二維積分 學數值計算的兄弟們可以看看 精度可以自己設定 具體文件里有說明
代碼片段和文件信息
%?龍貝格一維/二維積分公式。積分值=rombeg(‘函數‘XminXmax[YminYmax][精度隱含精度1e-8])
%?二維情況下可做變上下限積分(必須是匿名函數形式).此程序積分區間和函數可為矩陣
%?但兩者不能同時為矩陣。變上下限積分時只能y變量是矩陣計算效果等同x有矩陣情況
function?I=rombeg(fXminXmaxYminYmaxtol)
if?~isa(f‘function_handle‘)&&~isa(f‘inline‘)
???f=inline(f);
end
switch?nargin
????case?3?%一維積分
?????????I=jf1(fXminXmax);?%龍貝格一維積分計算函數
????case?4%龍貝格一維積分計算函數
????????I=jf1(fXminXmaxYmin);
????case?5??%二維積分
????h=Xmax-Xmin;
????F1=@(y)?f(Xminy);
????F2=@(y)?f(Xmaxy);
?????if?isa(Ymin‘function_handle‘)
???????c1=Ymin(Xmin);
???????c2=Ymin(Xmax);
?????else?c1=Ymin;c2=Ymin;
?????end
?????if?isa(Ymax‘function_handle‘)??
?????????d1=Ymax(Xmin);
?????????d2=Ymax(Xmax);
?????else?d1=Ymax;d2=Ymax;
?????end
????s1=jf1(F1c1d1);
????s2=jf1(F2c2d2);
????V(::1)=(s1+s2).*h/2;
????n=1;
????k=1;
????while?k<=10
????????n=2*n;
????????h=h/2;
????????k=k+1;
????????sum=zeros(size(s1));
????????for?p=1:n/2
????????????F=@(y)?f(Xmin+(2*p-1)*hy);
?????????????if?isa(Ymin‘function_handle‘)
????????????c=Ymin(Xmin+(2*p-1)*h);
?????????????else?c=Ymin;
?????????????end
?????????????if?isa(Ymax‘function_handle‘)??
????????????d=Ymax(Xmin+(2*p-1)*h);
?????????????else?d=Ymax;
?????????????end
????????????s=jf1(Fcd);
????????????sum=sum+s;
????????end
????????V(::k)=V(::k-1)/2+(sum.*h);
????????m=k;
??????????while?1%龍貝格遞推
????????????V1(::m-1)=(4*V(::m)-V(::m-1))/3;
????????????m=m-1;
?????????????if?m==1
??????????????break
?????????????else?V2(::m-1)=(8*V1(::m)-V1(::m-1))/7;
??????????????m=m-1;
?????????????end
?????????????if?m==1
?????????????????break
???????????????else?V3(::m-1)=(16*V2(::m)-V2(::m-1))/15;
?????????????????????m=m-1;
?????????????????????break
?????????????end
??????????end
??????????????if?k==4&&(max((max(abs(real(V3(::1)-V2(::2)))))))<=1e-8&&(max((max(abs(imag(V3(::1)-V2(::2)))))))<=1e-8%精度控制
?????????????????I=V3(::m);
????????????????break
?????????????elseif?k>4&&(max(max(abs(real(V3(::m)-V3(::m-1))))))<=1e-8&&(max((max(abs(imag(V3(::1)-V2(::2)))))))<=1e-8
?????????????????I=V3(::m);
??????????????break
??????????????end
????end
case?6
????h=Xmax-Xmin;
????F1=@(y)?f(Xminy);
????F2=@(y)?f(Xmaxy);
?????if?isa(Ymin‘function_handle‘)
???????c1=Ymin(Xmin);
???????c2=Ymin(Xmax);
?????else?c1=Ymin;c2=Ymin;
?????end
?????if?isa(Ymax‘function_handle‘)??
?????????d1=Ymax(Xmin);
?????????d2=Ymax(Xmax);
?????else?d1=Ymax;d2=Ymax;
?????end
????s1=jf1(F1c1d1);
????s2=jf1(F2c2d2);
????V(::1)=(s1+s2).*h/2;
????n=1;
????k=1;
????while?k<=10
????????n=2*n;
????????h=h/2;
????????k=k+1;
?????
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