| d0=: %@>:@(] % 100"_) #. |.@[ | Present value flows x at y% |
| d1=: >:@(] % 100"_) #. [ | Future value of flows x at interest rate y |
| d2=: ([: >: [ % 100"_) ^/ ] | Amount of 1 at x% for y periods |
| d3=: 13 : '|: y%-.(>:y) ^/ -x.' | Annuity coefficient: periods x at rate y |
| d4=: [ d3 [: m5 ] | Annuity coefficient: periods x at y % |
| m5=: 0.01&* | Rate from percent |
| m6=: 100&* | Percent from rate |
| d7=: <: @ ((^%)~ >:) | Modal rate from annual rate |
| d8=: stretch=: [ $ ] , ($ ,: @ {:) | Stretch y to length x |
| d9=: */\ @ (1&,) @ (stretch >:) | Accumulate at y for period x |
| m10=: (% {.) @ (|.@(+/\)@i.@>:) | Outstanding balances on rule of 78 |
| m11=: }.%}: | Rate of change from amounts |
| m12=: 2&((%~)/\) | Rate of change from amounts |
| d13=:4 :'r*+/\y%r=:*/\1,x.$~<:#y' | Accumulate deposits y at x |
| d14=: [+2: -/\ [: >./\ 0:,[: +/\ - | Work done; x=capacity, y=demand |
Convert an annual interest rate of 7% to a monthly rate.
]m=: 12 d7 0.07 0.00565415 (1 + m)^12 1.07
Calculate the amount of 1 for 5 periods at rates of 7% for the first two years and 6% thereafter. The function d9 uses d8 to fill out the term with the last given rate.
5 d9 0.07 0.07 0.06 1 1.07 1.1449 1.21359 1.28641 1.36359
Calculate the declining balances for a year for 1 using the rule of 78.
,.m10 12
1
0.846154
0.705128
0.576923
0.461538
0.358974
0.269231
0.192308
0.128205
0.0769231
0.0384615
0.0128205
0
x: m10 12
1 11r13 55r78 15r26 6r13 14r39 7r26 5r26 5r39 1r13 1r26 1r78 0
78 * m10 12
78 66 55 45 36 28 21 15 10 6 3 1 0
Calculate the balances after periodic payments of 100, 100, 200, and 200 are made at rates of 10%, 10%, and 5%.
1.10 1.10 1.05 m13 100 100 200 200 100 210 431 652.55