--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/finance/pv.m	Fri Oct 23 05:44:01 1998 +0000
@@ -0,0 +1,79 @@
+## Copyright (C) 1995, 1996  Kurt Hornik
+## 
+## This program is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 2, or (at your option)
+## any later version.
+## 
+## This program is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+## General Public License for more details. 
+## 
+## You should have received a copy of the GNU General Public License
+## along with this file.  If not, write to the Free Software Foundation,
+## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+## usage:  pv (r, n, p [, l] [, method])
+##
+## Returns the present value of an investment that will pay off p for n
+## consecutive periods, assuming an interest r.
+##
+## With the optional scalar argument l, one can specify an additional
+## lump-sum payment made at the end of n periods.
+##
+## With the optional string argument `method', one can specify whether
+## payments are made at the end ("e", default) or at the beginning ("b")
+## of each period.
+##
+## Note that the rate r is not specified in percent, i.e., one has to
+## write 0.05 rather than 5 %.
+##
+## See also:  pmt, nper, rate;  npv.
+  
+## Author:  KH <Kurt.Hornik@ci.tuwien.ac.at>
+## Description:  Present value of an investment
+
+function v = pv (r, n, p, l, m)
+  
+  if ((nargin < 3) || (nargin > 5))
+    usage ("pv (r, n, p [, l] [, method])");
+  endif
+  
+  if !(is_scalar (r) && (r > -1))
+    error ("pv:  r must be a scalar > -1");
+  elseif !(is_scalar (n) && (n > 0))
+    error ("pv:  n must be a positive scalar");
+  elseif !is_scalar (p)
+    error ("pv:  p must be a scalar.");
+  endif
+  
+  if (r != 0)
+    v = p * (1 - (1 + r)^(-n)) / r;
+  else
+    v = p * n;
+  endif
+  
+  if (nargin > 3)
+    if (nargin == 5)
+      if !isstr (m)
+	error ("pv:  `method' must be a string");
+      endif
+    elseif isstr (l)
+      m = l;
+      l = 0;
+    else
+      m = "e";
+    endif
+    if strcmp (m, "b")
+      v = v * (1 + r);
+    endif
+    if is_scalar (l)
+      v = v + pvl (r, n, l);
+    else
+      error ("pv:  l must be a scalar");
+    endif
+  endif
+  
+endfunction
+