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？
6 U$ l8 D' r7 ^+ A8 m7 f( d/ ~1 G5 c9 E# t其中一段的结果如下：

-6.577334937091747730665057507568065230549384834272368050884038839567853*10^273,
* y; \) i* X# Z0 T-5.139195757419310323174537703330917750350843564381075360877238710618581*10^291，
-Inf
$ n. `) c' {7 r9 `, TNaN
NaN
NaN

/ _' g6 n: N) w" z
7 ]7 W. U( n: o3 w5 [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)
; h+ y" v5 }' A& R%UNTITLED2 Summary of this function goes here
% Detailed explanation goes here
%x'=f(t,x,y) y'=g(t,x,y)
%N为迭代次数
0 E+ O! S& b, d%h为步长
! d5 s# @: }4 w( a6 K' _: d+ C%ya,xa为初值
B1=2.652e+005;A1=2.922;
6 i6 x+ k0 `# T* NB2=2.233e+005;A2=1.442;
R1=94.25;
" ^- O. `) p. ]& u) }& R/ Z" XC=6.897e-11;
2 p. D& ?# _9 [) R6 Y" ]L1=21.75e-6;
7 j. `+ o: e3 a* |3 ~%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);
) A" @& Y+ J. ]3 j# kf=@(t,x,y)((I-(x-((x-B1)/A1-y)*R1-B2)/A2-(x-B1)/A1)/C);
2 `. }4 K- R/ n: k" G; J5 Q) Xg=@(t,x,y)(((x-((x-B1)/A1-y)*R1-B2)/A2-y)*R1/L1);
) z: L; o: m4 T; ^$ Dh=(b-a)/N;
" v$ c# n3 Z7 F* m( dT=zeros(1,N+1);
X=zeros(1,N+1);
Y=zeros(1,N+1);
0 K8 G/ X& Z% L0 Y6 {( F' {& }" S* F% nT=a:h:b;
X(1)=xa;
! ~9 e9 e& o8 \# s' zY(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);
, _# s  @, v3 [" N9 of2=vpa(feval(f,T(j)+h/2,X(j)+h/2*f1,Y(j)+g1/2),90);
g2=vpa(feval(g,T(j)+h/2,X(j)+h/2*f1,Y(j)+h/2*g1),90);
, f+ k" u# f: g% [, m! T! D1 Bf3=vpa(feval(f,T(j)+h/2,X(j)+h/2*f2,Y(j)+h*g2/2),90);
. b" E, V) n3 e$ A/ H1 S& Sg3=vpa(feval(g,T(j)+h/2,X(j)+h/2*f2,Y(j)+h/2*g2),90);
f4=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);
' i" T5 N& j1 ^  V$ l" b9 }7 QX(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'];
; k- L& w) C& ^* D8 j+ Dend
+ ~  w$ e" P5 b3 f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~~~