/*************************************************************************
Rational least squares fitting using Floater-Hormann rational functions
with optimal D chosen from [0,9].
Equidistant grid with M node on [min(x),max(x)] is used to build basis
functions. Different values of D are tried, optimal D (least root mean
square error) is chosen. Task is linear, so linear least squares solver
is used. Complexity of this computational scheme is O(N*M^2) (mostly
dominated by the least squares solver).
INPUT PARAMETERS:
X - points, array[0..N-1].
Y - function values, array[0..N-1].
N - number of points, N>0.
M - number of basis functions ( = number_of_nodes), M>=2.
OUTPUT PARAMETERS:
Info- same format as in LSFitLinearWC() subroutine.
* Info>0 task is solved
* Info<=0 an error occured:
-4 means inconvergence of internal SVD
-3 means inconsistent constraints
B - barycentric interpolant.
Rep - report, same format as in LSFitLinearWC() subroutine.
Following fields are set:
* DBest best value of the D parameter
* RMSError rms error on the (X,Y).
* AvgError average error on the (X,Y).
* AvgRelError average relative error on the non-zero Y
* MaxError maximum error
NON-WEIGHTED ERRORS ARE CALCULATED
-- ALGLIB PROJECT --
Copyright 18.08.2009 by Bochkanov Sergey
*************************************************************************/
public static void barycentricfitfloaterhormann(double[] x, double[] y, int n, int m, out int info, out barycentricinterpolant b, out barycentricfitreport rep)
{
info = 0;
b = new barycentricinterpolant();
rep = new barycentricfitreport();
lsfit.barycentricfitfloaterhormann(x, y, n, m, ref info, b.innerobj, rep.innerobj);
return;
}
/*************************************************************************
Weghted rational least squares fitting using Floater-Hormann rational
functions with optimal D chosen from [0,9], with constraints and
individual weights.
Equidistant grid with M node on [min(x),max(x)] is used to build basis
functions. Different values of D are tried, optimal D (least WEIGHTED root
mean square error) is chosen. Task is linear, so linear least squares
solver is used. Complexity of this computational scheme is O(N*M^2)
(mostly dominated by the least squares solver).
SEE ALSO
* BarycentricFitFloaterHormann(), "lightweight" fitting without invididual
weights and constraints.
INPUT PARAMETERS:
X - points, array[0..N-1].
Y - function values, array[0..N-1].
W - weights, array[0..N-1]
Each summand in square sum of approximation deviations from
given values is multiplied by the square of corresponding
weight. Fill it by 1's if you don't want to solve weighted
task.
N - number of points, N>0.
XC - points where function values/derivatives are constrained,
array[0..K-1].
YC - values of constraints, array[0..K-1]
DC - array[0..K-1], types of constraints:
* DC[i]=0 means that S(XC[i])=YC[i]
* DC[i]=1 means that S'(XC[i])=YC[i]
SEE BELOW FOR IMPORTANT INFORMATION ON CONSTRAINTS
K - number of constraints, 0<=K<M.
K=0 means no constraints (XC/YC/DC are not used in such cases)
M - number of basis functions ( = number_of_nodes), M>=2.
OUTPUT PARAMETERS:
Info- same format as in LSFitLinearWC() subroutine.
* Info>0 task is solved
* Info<=0 an error occured:
-4 means inconvergence of internal SVD
-3 means inconsistent constraints
-1 means another errors in parameters passed
(N<=0, for example)
B - barycentric interpolant.
Rep - report, same format as in LSFitLinearWC() subroutine.
Following fields are set:
* DBest best value of the D parameter
* RMSError rms error on the (X,Y).
* AvgError average error on the (X,Y).
* AvgRelError average relative error on the non-zero Y
* MaxError maximum error
NON-WEIGHTED ERRORS ARE CALCULATED
IMPORTANT:
this subroitine doesn't calculate task's condition number for K<>0.
SETTING CONSTRAINTS - DANGERS AND OPPORTUNITIES:
Setting constraints can lead to undesired results, like ill-conditioned
behavior, or inconsistency being detected. From the other side, it allows
us to improve quality of the fit. Here we summarize our experience with
constrained barycentric interpolants:
* excessive constraints can be inconsistent. Floater-Hormann basis
functions aren't as flexible as splines (although they are very smooth).
* the more evenly constraints are spread across [min(x),max(x)], the more
chances that they will be consistent
* the greater is M (given fixed constraints), the more chances that
constraints will be consistent
* in the general case, consistency of constraints IS NOT GUARANTEED.
* in the several special cases, however, we CAN guarantee consistency.
* one of this cases is constraints on the function VALUES at the interval
boundaries. Note that consustency of the constraints on the function
DERIVATIVES is NOT guaranteed (you can use in such cases cubic splines
which are more flexible).
* another special case is ONE constraint on the function value (OR, but
not AND, derivative) anywhere in the interval
Our final recommendation is to use constraints WHEN AND ONLY WHEN you
can't solve your task without them. Anything beyond special cases given
above is not guaranteed and may result in inconsistency.
-- ALGLIB PROJECT --
Copyright 18.08.2009 by Bochkanov Sergey
*************************************************************************/
public static void barycentricfitfloaterhormannwc(ref double[] x,
ref double[] y,
ref double[] w,
int n,
ref double[] xc,
ref double[] yc,
ref int[] dc,
int k,
int m,
ref int info,
ref barycentricinterpolant b,
ref barycentricfitreport rep)
{
int d = 0;
int i = 0;
double wrmscur = 0;
//.........这里部分代码省略.........
/*************************************************************************
Fitting by polynomials in barycentric form. This function provides simple
unterface for unconstrained unweighted fitting. See PolynomialFitWC() if
you need constrained fitting.
Task is linear, so linear least squares solver is used. Complexity of this
computational scheme is O(N*M^2), mostly dominated by least squares solver
SEE ALSO:
PolynomialFitWC()
INPUT PARAMETERS:
X - points, array[0..N-1].
Y - function values, array[0..N-1].
N - number of points, N>0
* if given, only leading N elements of X/Y are used
* if not given, automatically determined from sizes of X/Y
M - number of basis functions (= polynomial_degree + 1), M>=1
OUTPUT PARAMETERS:
Info- same format as in LSFitLinearW() subroutine:
* Info>0 task is solved
* Info<=0 an error occured:
-4 means inconvergence of internal SVD
P - interpolant in barycentric form.
Rep - report, same format as in LSFitLinearW() subroutine.
Following fields are set:
* RMSError rms error on the (X,Y).
* AvgError average error on the (X,Y).
* AvgRelError average relative error on the non-zero Y
* MaxError maximum error
NON-WEIGHTED ERRORS ARE CALCULATED
NOTES:
you can convert P from barycentric form to the power or Chebyshev
basis with PolynomialBar2Pow() or PolynomialBar2Cheb() functions from
POLINT subpackage.
-- ALGLIB PROJECT --
Copyright 10.12.2009 by Bochkanov Sergey
*************************************************************************/
public static void polynomialfit(double[] x, double[] y, int n, int m, out int info, out barycentricinterpolant p, out polynomialfitreport rep)
{
info = 0;
p = new barycentricinterpolant();
rep = new polynomialfitreport();
lsfit.polynomialfit(x, y, n, m, ref info, p.innerobj, rep.innerobj);
return;
}
/*************************************************************************
Weighted fitting by polynomials in barycentric form, with constraints on
function values or first derivatives.
Small regularizing term is used when solving constrained tasks (to improve
stability).
Task is linear, so linear least squares solver is used. Complexity of this
computational scheme is O(N*M^2), mostly dominated by least squares solver
SEE ALSO:
PolynomialFit()
INPUT PARAMETERS:
X - points, array[0..N-1].
Y - function values, array[0..N-1].
W - weights, array[0..N-1]
Each summand in square sum of approximation deviations from
given values is multiplied by the square of corresponding
weight. Fill it by 1's if you don't want to solve weighted
task.
N - number of points, N>0.
* if given, only leading N elements of X/Y/W are used
* if not given, automatically determined from sizes of X/Y/W
XC - points where polynomial values/derivatives are constrained,
array[0..K-1].
YC - values of constraints, array[0..K-1]
DC - array[0..K-1], types of constraints:
* DC[i]=0 means that P(XC[i])=YC[i]
* DC[i]=1 means that P'(XC[i])=YC[i]
SEE BELOW FOR IMPORTANT INFORMATION ON CONSTRAINTS
K - number of constraints, 0<=K<M.
K=0 means no constraints (XC/YC/DC are not used in such cases)
M - number of basis functions (= polynomial_degree + 1), M>=1
OUTPUT PARAMETERS:
Info- same format as in LSFitLinearW() subroutine:
* Info>0 task is solved
* Info<=0 an error occured:
-4 means inconvergence of internal SVD
-3 means inconsistent constraints
P - interpolant in barycentric form.
Rep - report, same format as in LSFitLinearW() subroutine.
Following fields are set:
* RMSError rms error on the (X,Y).
* AvgError average error on the (X,Y).
* AvgRelError average relative error on the non-zero Y
* MaxError maximum error
NON-WEIGHTED ERRORS ARE CALCULATED
IMPORTANT:
this subroitine doesn't calculate task's condition number for K<>0.
NOTES:
you can convert P from barycentric form to the power or Chebyshev
basis with PolynomialBar2Pow() or PolynomialBar2Cheb() functions from
POLINT subpackage.
SETTING CONSTRAINTS - DANGERS AND OPPORTUNITIES:
Setting constraints can lead to undesired results, like ill-conditioned
behavior, or inconsistency being detected. From the other side, it allows
us to improve quality of the fit. Here we summarize our experience with
constrained regression splines:
* even simple constraints can be inconsistent, see Wikipedia article on
this subject: http://en.wikipedia.org/wiki/Birkhoff_interpolation
* the greater is M (given fixed constraints), the more chances that
constraints will be consistent
* in the general case, consistency of constraints is NOT GUARANTEED.
* in the one special cases, however, we can guarantee consistency. This
case is: M>1 and constraints on the function values (NOT DERIVATIVES)
Our final recommendation is to use constraints WHEN AND ONLY when you
can't solve your task without them. Anything beyond special cases given
above is not guaranteed and may result in inconsistency.
-- ALGLIB PROJECT --
Copyright 10.12.2009 by Bochkanov Sergey
*************************************************************************/
public static void polynomialfitwc(double[] x, double[] y, double[] w, int n, double[] xc, double[] yc, int[] dc, int k, int m, out int info, out barycentricinterpolant p, out polynomialfitreport rep)
{
info = 0;
p = new barycentricinterpolant();
rep = new polynomialfitreport();
lsfit.polynomialfitwc(x, y, w, n, xc, yc, dc, k, m, ref info, p.innerobj, rep.innerobj);
return;
}
/*************************************************************************
Extracts X/Y/W arrays from rational interpolant
INPUT PARAMETERS:
B - barycentric interpolant
OUTPUT PARAMETERS:
N - nodes count, N>0
X - interpolation nodes, array[0..N-1]
F - function values, array[0..N-1]
W - barycentric weights, array[0..N-1]
-- ALGLIB --
Copyright 17.08.2009 by Bochkanov Sergey
*************************************************************************/
public static void barycentricunpack(barycentricinterpolant b,
ref int n,
ref double[] x,
ref double[] y,
ref double[] w)
{
double v = 0;
int i_ = 0;
n = 0;
x = new double[0];
y = new double[0];
w = new double[0];
n = b.n;
x = new double[n];
y = new double[n];
w = new double[n];
v = b.sy;
for(i_=0; i_<=n-1;i_++)
{
x[i_] = b.x[i_];
}
for(i_=0; i_<=n-1;i_++)
{
y[i_] = v*b.y[i_];
}
for(i_=0; i_<=n-1;i_++)
{
w[i_] = b.w[i_];
}
}
public static void polynomialfitwc(double[] x, double[] y, double[] w, double[] xc, double[] yc, int[] dc, int m, out int info, out barycentricinterpolant p, out polynomialfitreport rep)
{
int n;
int k;
if( (ap.len(x)!=ap.len(y)) || (ap.len(x)!=ap.len(w)))
throw new alglibexception("Error while calling 'polynomialfitwc': looks like one of arguments has wrong size");
if( (ap.len(xc)!=ap.len(yc)) || (ap.len(xc)!=ap.len(dc)))
throw new alglibexception("Error while calling 'polynomialfitwc': looks like one of arguments has wrong size");
info = 0;
p = new barycentricinterpolant();
rep = new polynomialfitreport();
n = ap.len(x);
k = ap.len(xc);
lsfit.polynomialfitwc(x, y, w, n, xc, yc, dc, k, m, ref info, p.innerobj, rep.innerobj);
return;
}
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