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RK.UB
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1989-03-02
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540b
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22 lines
10 print fnRk(&fnY(),0,1,log(50+100*#i),100)
20 end
30 '
40 fnY(X,Y)
50 return(Y)
60 '
70 ' Runga Kutta for y'=f(x,y), y(x0)=y0, integrating in N equal
80 ' steps from x0 to x.
90 fnRk(&fnF(),X0,Y0,X,N)
100 local H,I,K0,K1,K2,K3
110 H=(X-X0)/N/2
120 for I=1 to N
130 K0=fnF(X0,Y0)
140 X0+=H
150 K1=fnF(X0,Y0+H*K0)
160 K2=fnF(X0,Y0+H*K1)
170 X0+=H
180 K3=fnF(X0,Y0+2*H*K2)
190 Y0+=H*(K0+2*K1+2*K2+K3)/3
200 next
210 return(Y0)