com.numericalmethod.suanshu.datastructure

Class MathTable

java.lang.Object

com.numericalmethod.suanshu.datastructure.MathTable

All Implemented Interfaces:

java.io.Serializable

public class MathTable
extends java.lang.Object
implements java.io.Serializable

A mathematical table consists of numbers showing the results of calculation with varying arguments. It can be used to simplify and drastically speed up computation. We use them to archive results for, for example, quantiles of difficult distribution functions, often computed by slow Monte Carlo simulation.

This implementation provides various ways of looking up a table, esp. when an index is not exactly found in the table.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	MathTable.Row A row is indexed by a number and contains multiple values.

Constructor Summary

Constructors

Constructor and Description
MathTable(int nColumns) Construct an empty table.
MathTable(java.lang.String... headers) Construct an empty table by headers.

Method Summary

Modifier and Type	Method and Description
void	addRow(double index, double[] values) Add a row to the table.
void	addRows(double[][] data) Add rows by a double[][].
double	get(double i, int j) Get a particular table entry at [i,j].
double	get(double i, java.lang.String header) Get a particular table entry at [i, "header"].
java.lang.String[]	getHeaders() Get the column names.
double[]	getIndices() Get a copy of the row indices.
MathTable.Row	getRowOnOrAfter(double i) Get the row corresponding to a row index.
MathTable.Row	getRowOnOrBefore(double i) Get the row corresponding to a row index.
java.util.Iterator<MathTable.Row>	getRowsOnOrAfter(double i) Get the rows having the row index value equal to or just bigger than i.
java.util.Iterator<MathTable.Row>	getRowsOnOrBefore(double i) Get the rows having the row index value equal to or just smaller than i.
int	nColumns() Get the number of columns in the table.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MathTable

public MathTable(java.lang.String... headers)

Construct an empty table by headers.

Parameters:

headers - the column names; they must be unique

MathTable

public MathTable(int nColumns)

Construct an empty table. The headers are given default names.

Parameters:

nColumns - the number of columns

Method Detail

getHeaders

public java.lang.String[] getHeaders()

Get the column names.

Returns:

the headers

nColumns

public int nColumns()

Get the number of columns in the table.

Returns:

the number of columns

addRow

public void addRow(double index,
                   double[] values)

Add a row to the table.

Parameters:

index - the row index

values - the row values

addRows

public void addRows(double[][] data)

Add rows by a double[][]. The first number in each row/double[] is the row index. For example,

 new double[][]{
 {1.0, 1.1, 1.2, 1.3},
 {2.0, 2.1, 2.2, 2.3},
 {3.0, 3.1, 3.2, 3.3},
 {4.0, 4.1, 4.2, 4.3}
 };
 

represents

 1.0: {1.1, 1.2, 1.3}//row 1
 2.0: {2.1, 2.2, 2.3}//row 2
 3.0: {3.1, 3.2, 3.3}//row 3
 4.0: {4.1, 4.2, 4.3}//row 4
 

Parameters:

data - a double[][] of table entries.

getIndices

public double[] getIndices()

Get a copy of the row indices.

Returns:

a copy of the row indices

getRowOnOrBefore

public MathTable.Row getRowOnOrBefore(double i)

Get the row corresponding to a row index. If there is no row matching the exact index, the row with the biggest index but smaller than the specified index is returned.

Parameters:

i - a row index

Returns:

the corresponding row

Throws:

java.util.NoSuchElementException - if i is smaller than the first row index

getRowOnOrAfter

public MathTable.Row getRowOnOrAfter(double i)

Get the row corresponding to a row index. If there is no row matching the exact value, the row with the smallest index value but bigger than the specified value is returned.

Parameters:

i - a row index

Returns:

the corresponding row

Throws:

java.util.NoSuchElementException - if i is bigger than the last row index value

getRowsOnOrBefore

public java.util.Iterator<MathTable.Row> getRowsOnOrBefore(double i)

Get the rows having the row index value equal to or just smaller than i. The returned Iterator allows iterating the rows in reversed order starting from the matching row.

Parameters:

i - the row index

Returns:

an Iterator of Rows at or above the matching row

getRowsOnOrAfter

public java.util.Iterator<MathTable.Row> getRowsOnOrAfter(double i)

Get the rows having the row index value equal to or just bigger than i. The returned Iterator allows iterating the rows starting from the matching row.

Parameters:

i - the row index

Returns:

an Iterator of Rows at or below the matching row

get

public double get(double i,
                  int j)

Get a particular table entry at [i,j]. If there is no matching row to i, by default, we use linear interpolation between the row above and below. If i is smaller than the first row index, we return the value at [1,j]. A subclass may override this behavior to customize interpolation.

Parameters:

i - a row index

j - a column index, counting from 1

Returns:

the value at [i,j]

Throws:

java.util.NoSuchElementException - if rowValue is outside the table range

get

public double get(double i,
                  java.lang.String header)

Get a particular table entry at [i, "header"]. If there is no matching row to i, by default, we use linear interpolation between the row above and below. If i is smaller than the first row index, we return the value at [1,"header"]. A subclass may override this behavior to customize interpolation.

Parameters:

i - a row value index

header - the column name

Returns:

the value at [i, "header"]

Throws:

java.util.NoSuchElementException - if i is outside the table range