intgausslager.m

数值积分的几种算法

function I = IntGaussLager(f,n,AK,XK)
if(n<6 && nargin == 2)
    AK = 0;
    XK = 0;
else
    I=sum(AK.*subs(sym(f),findsym(sym(f)),XK));
end

switch n
    case 2,
        I=0.853553*subs(sym(f),findsym(sym(f)),-0.585786)+...
            0.146447*subs(sym(f),findsym(sym(f)),3.414214);
        
    case 3,
        I=0.711093*subs(sym(f),findsym(sym(f)),0.415575)+...
            0.278518*subs(sym(f),findsym(sym(f)),2.294280)+...
            0.0103893*subs(sym(f),findsym(sym(f)),6.289945);
        
    case 4,
        I=0.603154*subs(sym(f),findsym(sym(f)),0.322548)+...
            0.357419*subs(sym(f),findsym(sym(f)),1.745761)+...
            0.0388879*subs(sym(f),findsym(sym(f)),4.536620)+...
            0.000539295*subs(sym(f),findsym(sym(f)),9.395071);
           
    case 5,
        I=0.521756*subs(sym(f),findsym(sym(f)),0.263560)+...
            0.398667*subs(sym(f),findsym(sym(f)),1.413403)+...
            0.0759424*subs(sym(f),findsym(sym(f)),3.596426)+...
            0.00361176*subs(sym(f),findsym(sym(f)),7.085810)+...
            0.0000233700*subs(sym(f),findsym(sym(f)),12.640801);  
end