java.lang.Object
- org.esa.snap.core.util.math.FXYSum

Direct Known Subclasses:

FXYSum.BiCubic, FXYSum.BiLinear, FXYSum.BiQuadric, FXYSum.Cubic, FXYSum.Linear, FXYSum.Quadric
```
public class FXYSum
extends Object
```
The class FXYSum represents a sum of function terms sum(c[i] * f[i](x,y), i=0, n-1) where the vector c is a double array of constant coefficients and the vector f is an array of functions of type FXY in x and y.
The vector c of constants is set by the approximate(double[][], int[]) method.
After vector c is set, the actual function values z(x,y) are retrieved using the computeZ(double, double) method.

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`static class`	`FXYSum.BiCubic`	Provides an optimized `computeZ` method for bi-cubic polynomials (order = 3+3).
`static class`	`FXYSum.BiLinear`	Provides an optimized `computeZ` method for bi-linear polynomials (order = 1+1).
`static class`	`FXYSum.BiQuadric`	Provides an optimized `computeZ` method for bi-quadric polynomials (order = 2+2).
`static class`	`FXYSum.Cubic`	Provides an optimized `computeZ` method for cubic polynomials (order = 3).
`static class`	`FXYSum.Linear`	Provides an optimized `computeZ` method for linear polynomials (order = 1).
`static class`	`FXYSum.Quadric`	Provides an optimized `computeZ` method for quadric polynomials (order = 2).

Field Summary

Fields
Modifier and Type	Field	Description
`static FXY[]`	`FXY_4TH`
`static FXY[]`	`FXY_BI_4TH`
`static FXY[]`	`FXY_BI_CUBIC`
`static FXY[]`	`FXY_BI_LINEAR`
`static FXY[]`	`FXY_BI_QUADRATIC`
`static FXY[]`	`FXY_CUBIC`
`static FXY[]`	`FXY_LINEAR`
`static FXY[]`	`FXY_QUADRATIC`

Constructor Summary

Constructors
Constructor	Description
`FXYSum(FXY[] functions)`	Constructs a new sum of terms sum(c[i] f[i](x,y), i=0, n-1)* for the given vector of functions.
`FXYSum(FXY[] functions, int order)`	Constructs a new sum of terms sum(c[i] f[i](x,y), i=0, n-1)* for the given vector of functions and a polynomial order.
`FXYSum(FXY[] functions, int order, double[] coefficients)`	Constructs a new sum of terms sum(c[i] f[i](x,y), i=0, n-1)* for the given vector of functions and a polynomial order.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`protected void`	`appendCFunctionCodeBody(String fname, String x, String y, StringBuffer sb)`
`protected void`	`appendCFunctionCodeEnd(String fname, String x, String y, StringBuffer sb)`
`protected void`	`appendCFunctionCodePart(StringBuffer sb, String part, String x, String y)`
`protected void`	`appendCFunctionCodeStart(String fname, String x, String y, StringBuffer sb)`
`void`	`approximate(double[][] data, int[] indices)`	Approximates the given data points x,y,z by this sum of function terms so that z ~ sum(c[i] f[i](x,y), i=0, n-1)*.
`double`	`computeZ(double x, double y)`	Computes this sum of function terms z(x,y) = sum(c[i] f[i](x,y), i=0, n-1)*.
`static double`	`computeZ(FXY[] f, double[] c, double x, double y)`	Computes z(x,y) = sum(c[i] f[i](x,y), i = 0, n - 1)*.
`String`	`createCFunctionCode(String fname, String x, String y)`	Returns this sum of function terms as human-readable C-code.
`static FXYSum`	`createCopy(FXYSum fxySum)`	Creates a copy of the given `fxySum`.
`static FXYSum`	`createFXYSum(int order, double[] coefficients)`	Creates a `FXYSum` by the given order and coefficients.
`double[]`	`getCoefficients()`	Gets the vector c of coefficient elements c[i].
`FXY[]`	`getFunctions()`	Gets the vector f of functions elements f[i](x,y).
`double`	`getMaxError()`	Gets the maximum, absolute error of the approximation.
`int`	`getNumTerms()`	Gets the number n of terms c[i] f[i](x,y)*.
`int`	`getOrder()`	Gets the polynomial order, if any.
`double`	`getRootMeanSquareError()`	Gets the root mean square error.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - FXY_LINEAR
```
public static final FXY[] FXY_LINEAR
```
  - FXY_BI_LINEAR
```
public static final FXY[] FXY_BI_LINEAR
```
  - FXY_QUADRATIC
```
public static final FXY[] FXY_QUADRATIC
```
  - FXY_BI_QUADRATIC
```
public static final FXY[] FXY_BI_QUADRATIC
```
  - FXY_CUBIC
```
public static final FXY[] FXY_CUBIC
```
  - FXY_BI_CUBIC
```
public static final FXY[] FXY_BI_CUBIC
```
  - FXY_4TH
```
public static final FXY[] FXY_4TH
```
  - FXY_BI_4TH
```
public static final FXY[] FXY_BI_4TH
```
- Constructor Detail
  - FXYSum
```
public FXYSum(FXY[] functions)
```
    Constructs a new sum of terms sum(c[i] * f[i](x,y), i=0, n-1) for the given vector of functions. The vector c is initally set to zero and will remeain zero until the method approximate(double[][], int[]) is performed with given data on this function sum.
    
    Parameters:
    
    functions - the vector F of functions
  - FXYSum
```
public FXYSum(FXY[] functions,
              int order)
```
    Constructs a new sum of terms sum(c[i] * f[i](x,y), i=0, n-1) for the given vector of functions and a polynomial order. The vector c is initally set to zero and will remeain zero until the method approximate(double[][], int[]) is performed with given data on this function sum.
    
    Parameters:
    
    functions - the vector F of functions
    
    order - the polynomial order (for descriptive purpose only), -1 if unknown
  - FXYSum
```
public FXYSum(FXY[] functions,
              int order,
              double[] coefficients)
```
    Constructs a new sum of terms sum(c[i] * f[i](x,y), i=0, n-1) for the given vector of functions and a polynomial order. The vector c is set by the coefficients parameter. The coefficients will be recalculated if the method approximate(double[][], int[]) is called.
    
    Parameters:
    
    functions - the vector F of functions
    
    order - the polynomial order (for descriptive purpose only), -1 if unknown
    
    coefficients - the vector c
- Method Detail
  - createFXYSum
```
public static FXYSum createFXYSum(int order,
                                  double[] coefficients)
```
    Creates a FXYSum by the given order and coefficients.
    Note: This factory method supprots only the creation of instances of the following FXYSum classes:
    
    FXYSum.Linear - order = 1 ; number of coefficients = 3
    
    FXYSum.BiLinear - order = 2 ; number of coefficients = 4
    
    FXYSum.Quadric - order = 2 ; number of coefficients = 6
    
    FXYSum.BiQuadric - order = 4 ; number of coefficients = 9
    
    FXYSum.Cubic - order = 3 ; number of coefficients = 10
    
    FXYSum.BiCubic - order = 6 ; number of coefficients = 16
    Parameters:
    
    order - the order of the sum
    
    coefficients - the coefficients
    
    Returns:
    
    returns a FXYSum instance, or null if the resulting instance is one of the supported.
  - createCopy
```
public static FXYSum createCopy(FXYSum fxySum)
```
    Creates a copy of the given fxySum.
    
    Parameters:
    
    fxySum - the FXYSum to copy
    
    Returns:
    
    a copy of the given FXYSum
  - getNumTerms
```
public final int getNumTerms()
```
    Gets the number n of terms c[i] * f[i](x,y).
    
    Returns:
    
    the number of function terms
  - getFunctions
```
public final FXY[] getFunctions()
```
    Gets the vector f of functions elements f[i](x,y).
    
    Returns:
    
    the vector F of functions
  - getCoefficients
```
public final double[] getCoefficients()
```
    Gets the vector c of coefficient elements c[i].
    
    Returns:
    
    the vector F of functions
  - getOrder
```
public int getOrder()
```
    Gets the polynomial order, if any.
    
    Returns:
    
    the polynomial order or -1 if unknown
  - getRootMeanSquareError
```
public double getRootMeanSquareError()
```
    Gets the root mean square error.
    
    Returns:
    
    the root mean square error
  - getMaxError
```
public double getMaxError()
```
    Gets the maximum, absolute error of the approximation.
    
    Returns:
    
    the maximum, absolute error
  - computeZ
```
public double computeZ(double x,
                       double y)
```
    Computes this sum of function terms z(x,y) = sum(c[i] * f[i](x,y), i=0, n-1). The method will return zero unless the approximate(double[][], int[]) is called in order to set the coefficient vector c.
    
    Parameters:
    
    x - the x value
    
    y - the y value
    
    Returns:
    
    the z value
    
    See Also:
    
    computeZ(FXY[], double[], double, double)
  - computeZ
```
public static double computeZ(FXY[] f,
                              double[] c,
                              double x,
                              double y)
```
    Computes z(x,y) = sum(c[i] * f[i](x,y), i = 0, n - 1).
    
    Parameters:
    
    f - the function vector
    
    c - the coeffcient vector
    
    x - the x value
    
    y - the y value
    
    Returns:
    
    the z value
  - approximate
```
public void approximate(double[][] data,
                        int[] indices)
```
    Approximates the given data points x,y,z by this sum of function terms so that z ~ sum(c[i] * f[i](x,y), i=0, n-1). The method also sets the error statistics which can then be retrieved by the getRootMeanSquareError() and getMaxError() methods.
    
    Parameters:
    
    data - an array of values of the form {{x1,y1,z1}, {x2,y2,z2}, {x3,y3,z3}, ...}
    
    indices - an array of coordinate indices, determining the indices of x, y and z within a data element. If null then indices defaults to the array {0, 1, 2}.
    
    See Also:
    
    Approximator.approximateFXY(double[][], int[], FXY[], double[]), Approximator.computeErrorStatistics(double[][], int[], FXY[], double[]), computeZ(double, double)
  - createCFunctionCode
```
public String createCFunctionCode(String fname,
                                  String x,
                                  String y)
```
    Returns this sum of function terms as human-readable C-code.
    
    Parameters:
    
    fname - the name of the function z(x,y) = sum(C[i]*F[i](x,y), i, n)
    
    x - the name of the x variable
    
    y - the name of the y variable
    
    Returns:
    
    the C-code
  - appendCFunctionCodeStart
```
protected void appendCFunctionCodeStart(String fname,
                                        String x,
                                        String y,
                                        StringBuffer sb)
```
  - appendCFunctionCodeBody
```
protected void appendCFunctionCodeBody(String fname,
                                       String x,
                                       String y,
                                       StringBuffer sb)
```
  - appendCFunctionCodeEnd
```
protected void appendCFunctionCodeEnd(String fname,
                                      String x,
                                      String y,
                                      StringBuffer sb)
```
  - appendCFunctionCodePart
```
protected void appendCFunctionCodePart(StringBuffer sb,
                                       String part,
                                       String x,
                                       String y)
```

Class FXYSum

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

FXY_LINEAR

FXY_BI_LINEAR

FXY_QUADRATIC

FXY_BI_QUADRATIC

FXY_CUBIC

FXY_BI_CUBIC

FXY_4TH

FXY_BI_4TH

Constructor Detail

FXYSum

FXYSum

FXYSum

Method Detail

createFXYSum

createCopy

getNumTerms

getFunctions

getCoefficients

getOrder

getRootMeanSquareError

getMaxError

computeZ

computeZ

approximate

createCFunctionCode

appendCFunctionCodeStart

appendCFunctionCodeBody

appendCFunctionCodeEnd

appendCFunctionCodePart