pvvar  Present value of varying cash flow.
    pvvar returns the net present value of a cash flow given the periodic interest rate.
 
    PV = pvvar(CF, RATE)
    PV = pvvar(CF, RATE, DF)
 
    Optional Inputs: DF
 
    Inputs:
      CF - A vector of varying cash flows. Include the initial investment as the initial cash flow value (a negative number). If CF is a matrix, each column is treated as a separate cash-flow stream.
 
      RATE - Periodic interest rate. Enter as a decimal fraction. If CF is a matrix, a scalar RATE is allowed when the same rate applies to all cash-flow streams in CF. When multiple cash-flow stream require different discount rates, RATE must be a vector whose length equals the number of columns in CF.
 
    Optional Inputs:
      DF - A vector of serial date numbers or date strings on which the cash flows occur. Specify DF when there are irregular (nonperiodic) cash flows. The default assumes CF contains regular (periodic) cash flows. If CF is a matrix and all cash-flow streams share the same dates, DF can be a vector whose length matches the number of rows in CF. Specify DF as a matrix of the same size as CF when different cash-flow streams have different payment dates.
 
    Outputs:
      PV - The net present value of a varying cash flow.
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    Example:
       Suppose an initial investment of $10,000 is made. The following cash flow represents the yearly income realized by the investment. The annual discount rate is 8%.
 
          Year 1    $2000
          Year 2    $1500
          Year 3    $3000
          Year 4    $3800
          Year 5    $5000
 
       To calculate the net present value of the periodic cash flow do the following (Note that the original investment payment is included as the first cash flow value):
 
          pv = pvvar([-10000 2000 1500 3000 3800 5000], .08)
          pv =
                 1715.39
 
       Suppose an investment of $10,000 returns the following series of cash flows at a discount rate of 9%.
 
          Cash Flow  Dates
          ---------  -----------------
          -10000  January 12, 1987
            2500  February 14, 1988
            2000  March 3, 1988
            3000  June 14, 1988
            4000  December 1, 1988
 
       The variables CF and DF are defined as follows:
 
          cf = [-10000; 2500; 2000; 3000; 4000];
          df = {'01/12/1987'
                '02/14/1988'
                '03/03/1988'
                '06/14/1988'
                '12/01/1988'};
 
          pv = pvvar(cf, .09, df)
          pv =
                 142.16
 
       The net present value of the same investment under different discount rates, say, 7%, 9%, and 11%, can be obtained in a single call
 
          pv = pvvar(repmat(cf,1,3), [.07 .09 .11], df)
 
       yielding present values of 419.01, 142.16 and -122.12, respectively.