PC-1211, PC-1250, etc. TVM

[Albert Chan]

(05-29-2024 09:17 PM)robve Wrote:  36 W=Y : GOSUB 39 : Y=P+K*M*U+F*S : RETURN

Instead of NPV = 0, solve NPMT = 0 for rate may be better.

10 B=1 @ N=40 @ P=900 @ M=-40 @ F=-1000
20 DEF FNF(I) @ S=(1+I)^(-N) @ U=(1-S)/I @ K=1+B*I
30 FNF=P+K*M*U+F*S @ END DEF ! NPV
40 V=.01 @ W=FNF(V) @ I=.02 @ Y=FNF(I)
50 H=I-V @ V=I @ I=I-H*Y/(Y-W) @ W=Y @ Y=FNF(I)
60 DISP 100*I,Y @ IF V/I+I/V<>2 THEN 50

>run
 3.55877069046      -223.49575008
 4.3407684864        -68.532154113
 4.68660450765      -10.546204073
 4.74950349013      -.604877167
 4.75333056057      -.005731135
 4.75336716844      -.000003149
 4.75336718857      -.000000001

>30 FNF=(P+F*S)/U+K*M @ END DEF ! NPMT
>run
 4.7203131853        -.2913219635
 4.75310902569      -.0022751338
 4.75336716699      -.0000001902
 4.75336718857      -.0000000001

For rate convergence, I use ratio, r + 1/r = 2
If r = 1-ε, r+1/r = 2 + ε^2 + ε^3 + ε^4 + ...