From fa080de7afc95aa1c19a6e6fc0e0708ced2eadc4 Mon Sep 17 00:00:00 2001
From: Joseph Hunkeler <jhunkeler@gmail.com>
Date: Wed, 8 Jul 2015 20:46:52 -0400
Subject: Initial commit

---
 math/deboor/l2err_io.f | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100644 math/deboor/l2err_io.f

(limited to 'math/deboor/l2err_io.f')

diff --git a/math/deboor/l2err_io.f b/math/deboor/l2err_io.f
new file mode 100644
index 00000000..ac7fcf01
--- /dev/null
+++ b/math/deboor/l2err_io.f
@@ -0,0 +1,69 @@
+      subroutine l2err ( prfun , ftau , error )
+c  from  * a practical guide to splines *  by c. de boor
+c  this routine is to be called in the main program  l 2 m a i n .
+calls subprogram  ppvalu(interv)
+c  this subroutine computes various errors of the current l2-approxi-
+c  mation , whose pp-repr. is contained in common block  approx  ,
+c  to the given data contained in common block	data . it prints out
+c  the average error  e r r l 1 , the l2-error	e r r l 2,  and the
+c  maximum error  e r r m a x .
+c
+c******  i n p u t  ******
+c  prfun  a hollerith string.  if prfun = 2hon, the routine prints out
+c	   the value of the approximation as well as its error at
+c	   every data point.
+c
+c******  o u t p u t  ******
+c  ftau(1), ..., ftau(ntau),  with  ftau(i)  the approximation	f at
+c	   tau(i), all i.
+c  error(1), ..., error(ntau),	with  error(i) = scale*(g - f)
+c	   at tau(i), all i. here,  s c a l e  equals  1. in case
+c	   prfun .ne. 2hon , or the abs.error is greater than 100 some-
+c	   where. otherwise, s c a l e	is such that the maximum of
+c	   abs(error))	over all  i  lies between  10  and  100. this
+c	   makes the printed output more illustrative.
+c
+      integer prfun,   ie,k,l,ll,ntau,on
+      real ftau(1),error(1),  break,coef,err,errmax,errl1,errl2
+     *			     ,gtau,scale,tau,totalw,weight
+c     dimension ftau(ntau),error(ntau)
+      real ppvalu
+c     parameter lpkmax=100,ntmax=200,ltkmax=2000
+c     common / data / ntau, tau(ntmax),gtau(ntmax),weight(ntmax),totalw
+c     common /approx/ break(lpkmax),coef(ltkmax),l,k
+      common / data / ntau, tau(200),gtau(200),weight(200),totalw
+      common /approx/ break(100),coef(2000),l,k
+      data on /2hon /
+      errl1 = 0.
+      errl2 = 0.
+      errmax = 0.
+      do 10 ll=1,ntau
+	 ftau(ll) = ppvalu (break, coef, l, k, tau(ll), 0 )
+	 error(ll) = gtau(ll) - ftau(ll)
+	 err = abs(error(ll))
+	 if (errmax .lt. err)	errmax = err
+	 errl1 = errl1 + err*weight(ll)
+   10	 errl2 = errl2 + err**2*weight(ll)
+      errl1 = errl1/totalw
+      errl2 = sqrt(errl2/totalw)
+      print 615,errl2,errl1,errmax
+  615 format(///21h least square error =,e20.6/
+     1		21h average error      =,e20.6/
+     2		21h maximum error      =,e20.6//)
+      if (prfun .ne. on)		return
+c     **  scale error curve and print  **
+      ie = 0
+      scale = 1.
+      if (errmax .ge. 10.)		go to 18
+      do 17 ie=1,9
+	 scale = scale*10.
+	 if (errmax*scale .ge. 10.)	go to 18
+   17	 continue
+   18 do 19 ll=1,ntau
+   19	 error(ll) = error(ll)*scale
+      print 620,ie,(ll,tau(ll),ftau(ll),error(ll),ll=1,ntau)
+  620 format(///14x,36happroximation and scaled error curve/7x,
+     110hdata point,7x,13happroximation,3x,16hdeviation x 10**,i1/
+     2(i4,f16.8,f16.8,f17.6))
+					return
+      end
-- 
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