在微分方程计算过程中，结果中出现NaN，是怎么回事

zhuce

解微分方程运行后，出现的结果先是逐渐变大的数据，然后是变为无穷大Inf，接着就是NaN，这是怎么回事？有哪位知道啊？
其中一段的结果如下：

-6.577334937091747730665057507568065230549384834272368050884038839567853*10^273,
: a9 s! F; O8 g/ g1 q: S& I/ e1 q$ L-5.139195757419310323174537703330917750350843564381075360877238710618581*10^291，
( }/ ?, v; ]( c" r+ H; f  X-Inf
- c0 ]7 [& _* P, a! YNaN
NaN
- T; L& Z/ \5 R! c" o' k" JNaN


是用龙格-库塔方法计算微分方程组得出的结果，程序如下：
function R = wffcz(f,g,a,b,xa,ya,N,I)
& _: t% @, V0 q0 q* q%UNTITLED2 Summary of this function goes here
# i2 Z9 l1 Y6 t' t" ~2 p8 Q% Detailed explanation goes here
%x'=f(t,x,y) y'=g(t,x,y)
2 ?$ z7 @" z: [! e& P%N为迭代次数
%h为步长
9 N& B; J" g  a%ya,xa为初值
B1=2.652e+005;A1=2.922;
! R9 ~2 s$ l! C, G& lB2=2.233e+005;A2=1.442;
# b+ s- T9 V* J6 c# u) q! [R1=94.25;
C=6.897e-11;
L1=21.75e-6;
6 }0 Y- [2 S, _0 G8 y- Y. I+ V%f=@(t,x,y)((25079999999999999898935095034332140556544638976*t^9 - 3116000000000000083537608917399754195861504*t^8 + 164799999999999990698756673337884147712*t^7 - 4823999999999999755901658355204096*t^6 + 83320000000000003537039785984*t^5 - 770099999999999994757120*t^4 + 3330000000000000000*t^3 - 94230000000000*t^2 + 1885000000*t + 1847/50-(x-((x-B1)/A1-y)*R1-B2)/A2-(x-B1)/A1)/C);
f=@(t,x,y)((I-(x-((x-B1)/A1-y)*R1-B2)/A2-(x-B1)/A1)/C);
$ b: h0 _0 Z* ], og=@(t,x,y)(((x-((x-B1)/A1-y)*R1-B2)/A2-y)*R1/L1);
& u, t1 u* \% ph=(b-a)/N;
T=zeros(1,N+1);
X=zeros(1,N+1);
! u7 u! b1 D: V" D7 BY=zeros(1,N+1);
T=a:h:b;
X(1)=xa;
0 g+ v$ D* P( l+ iY(1)=ya;
for j=1:N
f1=vpa(feval(f,T(j),X(j),Y(j)),90);
g1=vpa(feval(g,T(j),X(j),Y(j)),90);
- R0 t/ A+ A. [4 `f2=vpa(feval(f,T(j)+h/2,X(j)+h/2*f1,Y(j)+g1/2),90);
2 s; X5 ~* V. ]: lg2=vpa(feval(g,T(j)+h/2,X(j)+h/2*f1,Y(j)+h/2*g1),90);
f3=vpa(feval(f,T(j)+h/2,X(j)+h/2*f2,Y(j)+h*g2/2),90);
) \' G. U! w7 c3 E# a7 \g3=vpa(feval(g,T(j)+h/2,X(j)+h/2*f2,Y(j)+h/2*g2),90);
% c' r! u9 h0 G8 |. d" ^/ ~8 C$ p; Xf4=vpa(feval(f,T(j)+h,X(j)+h*f3,Y(j)+h*g3),90);
g4=vpa(feval(g,T(j)+h,X(j)+h*f3,Y(j)+h*g3),90);
X(j+1)=vpa(X(j)+h*(f1+2*f2+2*f3+f4)/6,90);
Y(j+1)=vpa(Y(j)+h*(g1+2*g2+2*g3+g4)/6,90);
R=[T' X' Y'];
end
就不知道是程序问题还是硬件问题

redplum

执行程序之前写一句“format long”,有可能是初值设的不好，另外为什么方程的系数这样大呢

athuhu

支持楼主~~~