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# numpy.rate

`numpy.``rate`(nper, pmt, pv, fv, when='end', guess=0.10000000000000001, tol=9.9999999999999995e-07, maxiter=100)

  Compute the rate of interest per period.

  Parameters: | nper : array_like Number of compounding periods pmt : array_like Payment pv : array_like Present value fv : array_like 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 maxiter : int, optional Maximum iterations in finding the solution

  Notes

  The rate of interest `rate` is computed by solving the equation:

      fv + pv*(1+rate)**nper + pmt*(1+rate*when)/rate * ((1+rate)**nper - 1) = 0

  or, if `rate = 0`:

      fv + pv + pmt * nper = 0

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