The routine and its subsidiaries will now return an error status as
supplied by PDA_XERMSG.
SUBROUTINE PDA_DPCOEF (L, C, TC, A, STATUS)
***BEGIN PROLOGUE PDA_DPCOEF
***PURPOSE Convert the PDA_DPOLFT coefficients to Taylor series form.
***LIBRARY SLATEC
***CATEGORY K1A1A2
***TYPE DOUBLE PRECISION (PCOEF-S, PDA_DPCOEF-D)
***KEYWORDS CURVE FITTING, DATA FITTING, LEAST SQUARES, POLYNOMIAL FIT
***AUTHOR Shampine, L. F., (SNLA)
Davenport, S. M., (SNLA)
***DESCRIPTION
Abstract
PDA_DPOLFT computes the least squares polynomial fit of degree L as
a sum of orthogonal polynomials. PDA_DPCOEF changes this fit to its
Taylor expansion about any point C , i.e. writes the polynomial
as a sum of powers of (X-C). Taking C=0. gives the polynomial
in powers of X, but a suitable non-zero C often leads to
polynomials which are better scaled and more accurately evaluated.
The parameters for PDA_DPCOEF are
INPUT -- All TYPE REAL variables are DOUBLE PRECISION
L - Indicates the degree of polynomial to be changed to
its Taylor expansion. To obtain the Taylor
coefficients in reverse order, input L as the
negative of the degree desired. The absolute value
of L must be less than or equal to NDEG, the highest
degree polynomial fitted by PDA_DPOLFT .
C - The point about which the Taylor expansion is to be
made.
A - Work and output array containing values from last
call to PDA_DPOLFT .
OUTPUT -- All TYPE REAL variables are DOUBLE PRECISION
TC - Vector containing the first LL+1 Taylor coefficients
where LL=ABS(L). If L.GT.0 , the coefficients are
in the usual Taylor series order, i.e.
P(X) = TC(1) + TC(2)*(X-C) + ... + TC(N+1)*(X-C)**N
If L .LT. 0, the coefficients are in reverse order,
i.e.
P(X) = TC(1)*(X-C)**N + ... + TC(N)*(X-C) + TC(N+1)
STATUS - Returned error status.
The status must be zero on entry. This
routine does not check the status on entry.
***REFERENCES L. F. Shampine, S. M. Davenport and R. E. Huddleston,
Curve fitting by polynomials in one variable, Report
SLA-74-0270, Sandia Laboratories, June 1974.
***ROUTINES CALLED PDA_DP1VLU
***REVISION HISTORY (YYMMDD)
740601 DATE WRITTEN
890531 Changed all specific intrinsics to generic. (WRB)
891006 Cosmetic changes to prologue. (WRB)
891006 REVISION DATE from Version 3.2
891214 Prologue converted to Version 4.0 format. (BAB)
920501 Reformatted the REFERENCES section. (WRB)
950404 Implement status. (HME)
950517 Return immediately if PDA_DP1VLU returns a status. (HME)
***END PROLOGUE PDA_DPCOEF