ptolemy.math

## Class Interpolation

• java.lang.Object
• ptolemy.math.Interpolation

• ```public class Interpolation
extends java.lang.Object```
This class provides algorithms to do interpolation. Currently, zero, first, and third order interpolations are supported. These are the interpolation orders most often used in practice. zero order interpolation holds the last reference value; first order does linear interpolation; and third order interpolation is based on the Hermite curves in chapter 11 of "Computer Graphic, Principles and Practice", by Foley, van Dam, Feiner and Hughes, 2nd ed. in C, 1996.

The setValues() method specifies the reference values as a double array. setIndexes() specifies the indexes of those values as an int array. These two arrays must have the same length, and the indexes must be increasing and non-negative; otherwise an exception will be thrown. The values are periodic if a positive period is set by setPeriod(). In this case, the period must be greater than the largest index, and values within the index range 0 to (period-1) are repeated indefinitely. If the period is zero, the values are not periodic, and the values outside the range of the indexes are considered to be 0.0. The interpolation order is set by setOrder().

The default reference values are {1.0, 0.0} and the indexes are {0, 1}. The default period is 2 and the order is 0.

Since:
Ptolemy II 0.4
Version:
\$Id: Interpolation.java 65768 2013-03-07 03:33:00Z cxh \$
Author:
Sarah Packman, Yuhong Xiong
Accepted Rating:
 red (cxh)
Proposed Rating:
 Yellow (yuhong)
• ### Constructor Summary

Constructors
Constructor and Description
`Interpolation()`
Construct an instance of Interpolation using the default parameters.
• ### Method Summary

All Methods
Modifier and Type Method and Description
`int[]` `getIndexes()`
Return the reference indexes.
`int` `getOrder()`
Return the interpolation order.
`int` `getPeriod()`
Return the value repetition period.
`double[]` `getValues()`
Return the reference values.
`double` `interpolate(int index)`
Return the interpolation result for the specified index.
`void` `setIndexes(int[] indexes)`
Set the reference indexes.
`void` `setOrder(int order)`
Set the interpolation order.
`void` `setPeriod(int period)`
Set the value repetition period.
`void` `setValues(double[] values)`
Set the reference values.
• ### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`
• ### Constructor Detail

• #### Interpolation

`public Interpolation()`
Construct an instance of Interpolation using the default parameters.
• ### Method Detail

• #### getIndexes

`public int[] getIndexes()`
Return the reference indexes.
Returns:
An int array.
`setIndexes(int[])`
• #### getOrder

`public int getOrder()`
Return the interpolation order.
Returns:
An int.
`setOrder(int)`
• #### getPeriod

`public int getPeriod()`
Return the value repetition period.
Returns:
An int.
`setPeriod(int)`
• #### getValues

`public double[] getValues()`
Return the reference values.
Returns:
An double array.
`setValues(double[])`
• #### interpolate

`public double interpolate(int index)`
Return the interpolation result for the specified index.
Parameters:
`index` - The point of interpolation. Can be negative
Returns:
A double.
Throws:
`java.lang.IllegalStateException` - If the index and value arrays do not have the same length, or the period is not 0 and not greater than the largest index.
• #### setIndexes

`public void setIndexes(int[] indexes)`
Set the reference indexes.
Parameters:
`indexes` - An int array.
Throws:
`java.lang.IllegalArgumentException` - If the argument array is not increasing and non-negative.
`getIndexes()`
• #### setOrder

`public void setOrder(int order)`
Set the interpolation order.
Parameters:
`order` - An int.
Throws:
`java.lang.IllegalArgumentException` - If the order is not 0, 1, or 3.
`getOrder()`
• #### setPeriod

`public void setPeriod(int period)`
Set the value repetition period.
Parameters:
`period` - An int.
Throws:
`java.lang.IllegalArgumentException` - If the period is negative.
`getPeriod()`
`public void setValues(double[] values)`
`values` - A double array.
`getValues()`