java.lang.Object
- gov.usgs.earthquake.nshmp.data.Interpolator

```
public abstract class Interpolator
extends Object
```
Utility class to perform linear and log interpolations. The methods of this class are designed to be fast and perform very little argument checking for monotonicity and the like. Results are undefined for x- and y-value arguments where size < 2.
Making some assumptions, interpolation is fairly straightforward. Most of the methods implemented here are designed to support interpolation (or derivation) of y-values keyed to monotonically increasing x-values. X-value interpolation requires knowing if y-values are increasing or decreasing. Assumptions and behaviors:
- No error checking for null, empty, single-valued arrays; or arrays of different lengths is performed. Buyer beware.
- X-value arrays are always assumed to be strictly monotonically ascending with no repeated values.
- Internally, binary search is used for y-value interpolation; linear search is used for x-value interpolation.
- Y-value interpolation will always extrapolate off the ends a sequence; this may change, or be configurable, in the future.
- X-value interpolation is predicated on y-values representing some form of cumulative distribution function, either increasing or decreasing (complementary), and must be specified as such. X-values are assumed to be increasing by default.
- X-value interpolation never extrapolates off the ends of a sequence and will always return 0 for out-of-range targets.
Presently, only single value interpolation of x-values is supported. The more common use case is to resample a sequence of y-values, which is supported.
Two static methods, findX(double, double, double, double, double) and findY(double, double, double, double, double), are the basis for all interpolation operations in this class. These two methods are point-order agnostic.
Author:

U.S. Geological Survey

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static class Interpolator.Builder
An interpolator builder.

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`static Interpolator.Builder`	`builder()`	Create a new builder instance.
`abstract double`	`findX(double[] xs, double[] ys, double y)`	Return an interpolated x-value corresponding to the supplied y-value in the supplied x- and y-value arrays.
`static double`	`findX(double x1, double y1, double x2, double y2, double y)`	Return an interpolated or extrapolated x-value corresponding to the supplied y-value.
`abstract double`	`findX(XySequence xy, double y)`	Return an interpolated x-value corresponding to the supplied y-value in the supplied xy-sequence.
`abstract double`	`findX(List<Double> xs, List<Double> ys, double y)`	Return an interpolated x-value corresponding to the supplied y-value in the supplied x- and y-value arrays.
`abstract double`	`findY(double[] xs, double[] ys, double x)`	Return an interpolated or extrapolated y-value corresponding to the supplied x-value in the supplied x- and y-value arrays.
`abstract double[]`	`findY(double[] xs, double[] ys, double[] x)`	Return interpolated or extrapolated y-values using the supplied x- and y-value arrays.
`static double`	`findY(double x1, double y1, double x2, double y2, double x)`	Return an interpolated or extrapolated y-value corresponding to the supplied x-value.
`abstract double`	`findY(XySequence xy, double x)`	Return an interpolated or extrapolated y-value corresponding to the supplied x-value in the supplied xy-sequence.
`abstract double[]`	`findY(XySequence xy, double[] x)`	Return interpolated or extrapolated y-values using the supplied x- and y-value arrays.
`abstract double`	`findY(List<Double> xs, List<Double> ys, double x)`	Return an interpolated or extrapolated y-value corresponding to the supplied x-value in the supplied x- and y-value arrays.
`abstract double[]`	`findY(List<Double> xs, List<Double> ys, double[] x)`	Return interpolated or extrapolated y-values using the supplied x- and y-value arrays.

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

- Method Detail
  - findX
```
public static double findX(double x1,
                           double y1,
                           double x2,
                           double y2,
                           double y)
```
    Return an interpolated or extrapolated x-value corresponding to the supplied y-value. If any supplied value is NaN, returned value will also be NaN. Method does not perform any input validation such that if the supplied points are coincident or define a horizontal line, the method may return Infinity, -Infinity, or NaN.
    
    Parameters:
    
    x1 - x-value of first point
    
    y1 - y-value of first point
    
    x2 - x-value of second point
    
    y2 - y-value of second point
    
    y - value at which to find x
    
    Returns:
    
    the interpolated x-value
  - findX
```
public abstract double findX(double[] xs,
                             double[] ys,
                             double y)
```
    Return an interpolated x-value corresponding to the supplied y-value in the supplied x- and y-value arrays.
    
    Parameters:
    
    xs - x-values of a sequence
    
    ys - y-values of a sequence
    
    y - value at which to find x
    
    Returns:
    
    an interpolated x-value
  - findX
```
public abstract double findX(List<Double> xs,
                             List<Double> ys,
                             double y)
```
    Return an interpolated x-value corresponding to the supplied y-value in the supplied x- and y-value arrays.
    
    Parameters:
    
    xs - x-values of a sequence
    
    ys - y-values of a sequence
    
    y - value at which to find x
    
    Returns:
    
    an interpolated x-value
  - findX
```
public abstract double findX(XySequence xy,
                             double y)
```
    Return an interpolated x-value corresponding to the supplied y-value in the supplied xy-sequence.
    
    Parameters:
    
    xy - an xy-sequence
    
    y - value at which to find x
    
    Returns:
    
    an interpolated x-value
  - findY
```
public static double findY(double x1,
                           double y1,
                           double x2,
                           double y2,
                           double x)
```
    Return an interpolated or extrapolated y-value corresponding to the supplied x-value. If any supplied value is NaN, returned value will also be NaN. Method does not perform any input validation such that if the supplied points are coincident or define a vertical line, the method may return Infinity, -Infinity, or NaN.
    
    Parameters:
    
    x1 - x-value of first point
    
    y1 - y-value of first point
    
    x2 - x-value of second point
    
    y2 - y-value of second point
    
    x - value at which to find y
    
    Returns:
    
    an interpolated y-value
  - findY
```
public abstract double findY(double[] xs,
                             double[] ys,
                             double x)
```
    Return an interpolated or extrapolated y-value corresponding to the supplied x-value in the supplied x- and y-value arrays.
    
    Parameters:
    
    xs - x-values of a sequence
    
    ys - y-values of a sequence
    
    x - value at which to find y
    
    Returns:
    
    an interpolated y-value
  - findY
```
public abstract double findY(List<Double> xs,
                             List<Double> ys,
                             double x)
```
    Return an interpolated or extrapolated y-value corresponding to the supplied x-value in the supplied x- and y-value arrays.
    
    Parameters:
    
    xs - x-values of a sequence
    
    ys - y-values of a sequence
    
    x - value at which to find y
    
    Returns:
    
    an interpolated y-value
  - findY
```
public abstract double findY(XySequence xy,
                             double x)
```
    Return an interpolated or extrapolated y-value corresponding to the supplied x-value in the supplied xy-sequence.
    
    Parameters:
    
    xy - an xy-sequence
    
    x - value at which to find y
    
    Returns:
    
    an interpolated y-value
  - findY
```
public abstract double[] findY(double[] xs,
                               double[] ys,
                               double[] x)
```
    Return interpolated or extrapolated y-values using the supplied x- and y-value arrays.
    
    Parameters:
    
    xs - x-values of a sequence
    
    ys - y-values of a sequence
    
    x - values at which to find y-values
    
    Returns:
    
    interpolated y-values
  - findY
```
public abstract double[] findY(List<Double> xs,
                               List<Double> ys,
                               double[] x)
```
    Return interpolated or extrapolated y-values using the supplied x- and y-value arrays.
    
    Parameters:
    
    xs - x-values of a sequence
    
    ys - y-values of a sequence
    
    x - values at which to find y-values
    
    Returns:
    
    interpolated y-values
  - findY
```
public abstract double[] findY(XySequence xy,
                               double[] x)
```
    Return interpolated or extrapolated y-values using the supplied x- and y-value arrays.
    
    Parameters:
    
    xy - an xy-sequence
    
    x - values at which to find y-values
    
    Returns:
    
    interpolated y-values
  - builder
```
public static Interpolator.Builder builder()
```
    Create a new builder instance.

Class Interpolator

Nested Class Summary

Method Summary

Methods inherited from class java.lang.Object

Method Detail

findX

findX

findX

findX

findY

findY

findY

findY

findY

findY

findY

builder