diff options
Diffstat (limited to 'numpy/lib/financial.py')
| -rw-r--r-- | numpy/lib/financial.py | 93 |
1 files changed, 58 insertions, 35 deletions
diff --git a/numpy/lib/financial.py b/numpy/lib/financial.py index 95942da16..06fa1bd92 100644 --- a/numpy/lib/financial.py +++ b/numpy/lib/financial.py @@ -7,9 +7,13 @@ so that the functions behave like ufuncs with broadcasting and being able to be called with scalars or arrays (or other sequences). +Functions support the :class:`decimal.Decimal` type unless +otherwise stated. """ from __future__ import division, absolute_import, print_function +from decimal import Decimal + import numpy as np __all__ = ['fv', 'pmt', 'nper', 'ipmt', 'ppmt', 'pv', 'rate', @@ -32,7 +36,6 @@ def _convert_when(when): except (KeyError, TypeError): return [_when_to_num[x] for x in when] - def fv(rate, nper, pmt, pv, when='end'): """ Compute the future value. @@ -117,10 +120,8 @@ def fv(rate, nper, pmt, pv, when='end'): when = _convert_when(when) (rate, nper, pmt, pv, when) = map(np.asarray, [rate, nper, pmt, pv, when]) temp = (1+rate)**nper - miter = np.broadcast(rate, nper, pmt, pv, when) - zer = np.zeros(miter.shape) - fact = np.where(rate == zer, nper + zer, - (1 + rate*when)*(temp - 1)/rate + zer) + fact = np.where(rate == 0, nper, + (1 + rate*when)*(temp - 1)/rate) return -(pv*temp + pmt*fact) def pmt(rate, nper, pv, fv=0, when='end'): @@ -209,17 +210,18 @@ def pmt(rate, nper, pv, fv=0, when='end'): when = _convert_when(when) (rate, nper, pv, fv, when) = map(np.array, [rate, nper, pv, fv, when]) temp = (1 + rate)**nper - mask = (rate == 0.0) - masked_rate = np.where(mask, 1.0, rate) - z = np.zeros(np.broadcast(masked_rate, nper, pv, fv, when).shape) - fact = np.where(mask != z, nper + z, - (1 + masked_rate*when)*(temp - 1)/masked_rate + z) + mask = (rate == 0) + masked_rate = np.where(mask, 1, rate) + fact = np.where(mask != 0, nper, + (1 + masked_rate*when)*(temp - 1)/masked_rate) return -(fv + pv*temp) / fact def nper(rate, pmt, pv, fv=0, when='end'): """ Compute the number of periodic payments. + :class:`decimal.Decimal` type is not supported. + Parameters ---------- rate : array_like @@ -271,20 +273,18 @@ def nper(rate, pmt, pv, fv=0, when='end'): use_zero_rate = False with np.errstate(divide="raise"): try: - z = pmt*(1.0+rate*when)/rate + z = pmt*(1+rate*when)/rate except FloatingPointError: use_zero_rate = True if use_zero_rate: - return (-fv + pv) / (pmt + 0.0) + return (-fv + pv) / pmt else: - A = -(fv + pv)/(pmt+0.0) - B = np.log((-fv+z) / (pv+z))/np.log(1.0+rate) - miter = np.broadcast(rate, pmt, pv, fv, when) - zer = np.zeros(miter.shape) - return np.where(rate == zer, A + zer, B + zer) + 0.0 + A = -(fv + pv)/(pmt+0) + B = np.log((-fv+z) / (pv+z))/np.log(1+rate) + return np.where(rate == 0, A, B) -def ipmt(rate, per, nper, pv, fv=0.0, when='end'): +def ipmt(rate, per, nper, pv, fv=0, when='end'): """ Compute the interest portion of a payment. @@ -374,7 +374,7 @@ def ipmt(rate, per, nper, pv, fv=0.0, when='end'): ipmt = _rbl(rate, per, total_pmt, pv, when)*rate try: ipmt = np.where(when == 1, ipmt/(1 + rate), ipmt) - ipmt = np.where(np.logical_and(when == 1, per == 1), 0.0, ipmt) + ipmt = np.where(np.logical_and(when == 1, per == 1), 0, ipmt) except IndexError: pass return ipmt @@ -388,7 +388,7 @@ def _rbl(rate, per, pmt, pv, when): """ return fv(rate, (per - 1), pmt, pv, when) -def ppmt(rate, per, nper, pv, fv=0.0, when='end'): +def ppmt(rate, per, nper, pv, fv=0, when='end'): """ Compute the payment against loan principal. @@ -416,7 +416,7 @@ def ppmt(rate, per, nper, pv, fv=0.0, when='end'): total = pmt(rate, nper, pv, fv, when) return total - ipmt(rate, per, nper, pv, fv, when) -def pv(rate, nper, pmt, fv=0.0, when='end'): +def pv(rate, nper, pmt, fv=0, when='end'): """ Compute the present value. @@ -505,9 +505,7 @@ def pv(rate, nper, pmt, fv=0.0, when='end'): when = _convert_when(when) (rate, nper, pmt, fv, when) = map(np.asarray, [rate, nper, pmt, fv, when]) temp = (1+rate)**nper - miter = np.broadcast(rate, nper, pmt, fv, when) - zer = np.zeros(miter.shape) - fact = np.where(rate == zer, nper+zer, (1+rate*when)*(temp-1)/rate+zer) + fact = np.where(rate == 0, nper, (1+rate*when)*(temp-1)/rate) return -(fv + pmt*fact)/temp # Computed with Sage @@ -529,7 +527,7 @@ def _g_div_gp(r, n, p, x, y, w): # where # g(r) is the formula # g'(r) is the derivative with respect to r. -def rate(nper, pmt, pv, fv, when='end', guess=0.10, tol=1e-6, maxiter=100): +def rate(nper, pmt, pv, fv, when='end', guess=None, tol=None, maxiter=100): """ Compute the rate of interest per period. @@ -545,10 +543,10 @@ def rate(nper, pmt, pv, fv, when='end', guess=0.10, tol=1e-6, maxiter=100): Future value when : {{'begin', 1}, {'end', 0}}, {string, int}, optional When payments are due ('begin' (1) or 'end' (0)) - guess : float, optional - Starting guess for solving the rate of interest - tol : float, optional - Required tolerance for the solution + guess : Number, optional + Starting guess for solving the rate of interest, default 0.1 + tol : Number, optional + Required tolerance for the solution, default 1e-6 maxiter : int, optional Maximum iterations in finding the solution @@ -573,15 +571,26 @@ def rate(nper, pmt, pv, fv, when='end', guess=0.10, tol=1e-6, maxiter=100): """ when = _convert_when(when) + default_type = Decimal if isinstance(pmt, Decimal) else float + + # Handle casting defaults to Decimal if/when pmt is a Decimal and + # guess and/or tol are not given default values + if guess is None: + guess = default_type('0.1') + + if tol is None: + tol = default_type('1e-6') + (nper, pmt, pv, fv, when) = map(np.asarray, [nper, pmt, pv, fv, when]) + rn = guess - iter = 0 + iterator = 0 close = False - while (iter < maxiter) and not close: + while (iterator < maxiter) and not close: rnp1 = rn - _g_div_gp(rn, nper, pmt, pv, fv, when) diff = abs(rnp1-rn) close = np.all(diff < tol) - iter += 1 + iterator += 1 rn = rnp1 if not close: # Return nan's in array of the same shape as rn @@ -597,6 +606,8 @@ def irr(values): that gives a net present value of 0.0; for a more complete explanation, see Notes below. + :class:`decimal.Decimal` type is not supported. + Parameters ---------- values : array_like, shape(N,) @@ -650,6 +661,11 @@ def irr(values): (Compare with the Example given for numpy.lib.financial.npv) """ + # `np.roots` call is why this function does not support Decimal type. + # + # Ultimately Decimal support needs to be added to np.roots, which has + # greater implications on the entire linear algebra module and how it does + # eigenvalue computations. res = np.roots(values[::-1]) mask = (res.imag == 0) & (res.real > 0) if not mask.any(): @@ -657,7 +673,7 @@ def irr(values): res = res[mask].real # NPV(rate) = 0 can have more than one solution so we return # only the solution closest to zero. - rate = 1.0/res - 1 + rate = 1/res - 1 rate = rate.item(np.argmin(np.abs(rate))) return rate @@ -727,12 +743,19 @@ def mirr(values, finance_rate, reinvest_rate): Modified internal rate of return """ - values = np.asarray(values, dtype=np.double) + values = np.asarray(values) n = values.size + + # Without this explicit cast the 1/(n - 1) computation below + # becomes a float, which causes TypeError when using Decimal + # values. + if isinstance(finance_rate, Decimal): + n = Decimal(n) + pos = values > 0 neg = values < 0 if not (pos.any() and neg.any()): return np.nan numer = np.abs(npv(reinvest_rate, values*pos)) denom = np.abs(npv(finance_rate, values*neg)) - return (numer/denom)**(1.0/(n - 1))*(1 + reinvest_rate) - 1 + return (numer/denom)**(1/(n - 1))*(1 + reinvest_rate) - 1 |