org.apache.mahout.math

## Interface Vector

• ### Nested Class Summary

Nested Classes
Modifier and Type Interface and Description
`static interface ` `Vector.Element`
A holder for information about a specific item in the Vector.
• ### Method Summary

All Methods
Modifier and Type Method and Description
`double` ```aggregate(DoubleDoubleFunction aggregator, DoubleFunction map)```
Examples speak louder than words: aggregate(plus, pow(2)) is another way to say getLengthSquared(), aggregate(max, abs) is norm(Double.POSITIVE_INFINITY).
`double` ```aggregate(Vector other, DoubleDoubleFunction aggregator, DoubleDoubleFunction combiner)```
Generalized inner product - take two vectors, iterate over them both, using the combiner to combine together (and possibly map in some way) each pair of values, which are then aggregated with the previous accumulated value in the combiner.
`Iterable<Vector.Element>` `all()`
`String` `asFormatString()`
`Vector` `assign(double value)`
Assign the value to all elements of the receiver
`Vector` `assign(double[] values)`
Assign the values to the receiver
`Vector` ```assign(DoubleDoubleFunction f, double y)```
Apply the function to each element of the receiver, using the y value as the second argument of the DoubleDoubleFunction
`Vector` `assign(DoubleFunction function)`
Apply the function to each element of the receiver
`Vector` `assign(Vector other)`
Assign the other vector values to the receiver
`Vector` ```assign(Vector other, DoubleDoubleFunction function)```
Apply the function to each element of the receiver and the corresponding element of the other argument
`Vector` `clone()`
Return a copy of the recipient
`Matrix` `cross(Vector other)`
Return the cross product of the receiver and the other vector
`Vector` `divide(double x)`
Return a new vector containing the values of the recipient divided by the argument
`double` `dot(Vector x)`
Return the dot product of the recipient and the argument
`double` `get(int index)`
Return the value at the given index
`double` `getDistanceSquared(Vector v)`
Get the square of the distance between this vector and the other vector.
`Vector.Element` `getElement(int index)`
Return an object of Vector.Element representing an element of this Vector.
`double` `getIteratorAdvanceCost()`
Gets an estimate of the cost (in number of operations) it takes to advance an iterator through the nonzero elements of this vector.
`double` `getLengthSquared()`
Return the sum of squares of all elements in the vector.
`double` `getLookupCost()`
Gets an estimate of the cost (in number of operations) it takes to lookup a random element in this vector.
`int` `getNumNondefaultElements()`
Return the number of values in the recipient which are not the default value.
`int` `getNumNonZeroElements()`
Return the number of non zero elements in the vector.
`double` `getQuick(int index)`
Return the value at the given index, without checking bounds
`void` ```incrementQuick(int index, double increment)```
Increment the value at the given index by the given value.
`boolean` `isAddConstantTime()`
Return true iff adding a new (nonzero) element takes constant time for this vector.
`boolean` `isDense()`
true if this implementation should be considered dense -- that it explicitly represents every value
`boolean` `isSequentialAccess()`
true if this implementation should be considered to be iterable in index order in an efficient way.
`Vector` `like()`
Return an empty vector of the same underlying class as the receiver
`Vector` `like(int cardinality)`
Return a new empty vector of the same underlying class as the receiver with given cardinality
`Vector` `logNormalize()`
Return a new vector containing the log(1 + entry)/ L_2 norm values of the recipient
`Vector` `logNormalize(double power)`
Return a new Vector with a normalized value calculated as log_power(1 + entry)/ L_power norm.
`double` `maxValue()`
`int` `maxValueIndex()`
`void` `mergeUpdates(OrderedIntDoubleMapping updates)`
Merge a set of (index, value) pairs into the vector.
`Vector` `minus(Vector x)`
Return a new vector containing the element by element difference of the recipient and the argument
`double` `minValue()`
`int` `minValueIndex()`
`Iterable<Vector.Element>` `nonZeroes()`
`double` `norm(double power)`
Return the k-norm of the vector.
`Vector` `normalize()`
Return a new vector containing the normalized (L_2 norm) values of the recipient
`Vector` `normalize(double power)`
Return a new Vector containing the normalized (L_power norm) values of the recipient.
`Vector` `plus(double x)`
Return a new vector containing the sum of each value of the recipient and the argument
`Vector` `plus(Vector x)`
Return a new vector containing the element by element sum of the recipient and the argument
`void` ```set(int index, double value)```
Set the value at the given index
`void` ```setQuick(int index, double value)```
Set the value at the given index, without checking bounds
`int` `size()`
Return the cardinality of the recipient (the maximum number of values)
`Vector` `times(double x)`
Return a new vector containing the product of each value of the recipient and the argument
`Vector` `times(Vector x)`
Return a new vector containing the element-wise product of the recipient and the argument
`Vector` ```viewPart(int offset, int length)```
Return a new vector containing the subset of the recipient
`double` `zSum()`
Return the sum of all the elements of the receiver
• ### Method Detail

• #### asFormatString

`String asFormatString()`
Returns:
a formatted String suitable for output
• #### assign

`Vector assign(double value)`
Assign the value to all elements of the receiver
Parameters:
`value` - a double value
Returns:
• #### assign

`Vector assign(double[] values)`
Assign the values to the receiver
Parameters:
`values` - a double[] of values
Returns:
Throws:
`CardinalityException` - if the cardinalities differ
• #### assign

`Vector assign(Vector other)`
Assign the other vector values to the receiver
Parameters:
`other` - a Vector
Returns:
Throws:
`CardinalityException` - if the cardinalities differ
• #### assign

`Vector assign(DoubleFunction function)`
Apply the function to each element of the receiver
Parameters:
`function` - a DoubleFunction to apply
Returns:
• #### assign

```Vector assign(Vector other,
DoubleDoubleFunction function)```
Apply the function to each element of the receiver and the corresponding element of the other argument
Parameters:
`other` - a Vector containing the second arguments to the function
`function` - a DoubleDoubleFunction to apply
Returns:
Throws:
`CardinalityException` - if the cardinalities differ
• #### assign

```Vector assign(DoubleDoubleFunction f,
double y)```
Apply the function to each element of the receiver, using the y value as the second argument of the DoubleDoubleFunction
Parameters:
`f` - a DoubleDoubleFunction to be applied
`y` - a double value to be argument to the function
Returns:
• #### size

`int size()`
Return the cardinality of the recipient (the maximum number of values)
Returns:
an int
• #### isDense

`boolean isDense()`
true if this implementation should be considered dense -- that it explicitly represents every value
Returns:
true or false
• #### isSequentialAccess

`boolean isSequentialAccess()`
true if this implementation should be considered to be iterable in index order in an efficient way. In particular this implies that `all()` and `nonZeroes()` ()} return elements in ascending order by index.
Returns:
true iff this implementation should be considered to be iterable in index order in an efficient way.
• #### clone

`Vector clone()`
Return a copy of the recipient
Returns:
a new Vector
• #### all

`Iterable<Vector.Element> all()`
• #### nonZeroes

`Iterable<Vector.Element> nonZeroes()`
• #### getElement

`Vector.Element getElement(int index)`
Return an object of Vector.Element representing an element of this Vector. Useful when designing new iterator types.
Parameters:
`index` - Index of the Vector.Element required
Returns:
The Vector.Element Object

`void mergeUpdates(OrderedIntDoubleMapping updates)`
Merge a set of (index, value) pairs into the vector.
Parameters:
`updates` - an ordered mapping of indices to values to be merged in.
• #### divide

`Vector divide(double x)`
Return a new vector containing the values of the recipient divided by the argument
Parameters:
`x` - a double value
Returns:
a new Vector
• #### dot

`double dot(Vector x)`
Return the dot product of the recipient and the argument
Parameters:
`x` - a Vector
Returns:
a new Vector
Throws:
`CardinalityException` - if the cardinalities differ
• #### get

`double get(int index)`
Return the value at the given index
Parameters:
`index` - an int index
Returns:
the double at the index
Throws:
`IndexException` - if the index is out of bounds
• #### getQuick

`double getQuick(int index)`
Return the value at the given index, without checking bounds
Parameters:
`index` - an int index
Returns:
the double at the index
• #### like

`Vector like()`
Return an empty vector of the same underlying class as the receiver
Returns:
a Vector
• #### like

`Vector like(int cardinality)`
Return a new empty vector of the same underlying class as the receiver with given cardinality
Parameters:
`cardinality` - - size of vector
Returns:
`Vector`
• #### minus

`Vector minus(Vector x)`
Return a new vector containing the element by element difference of the recipient and the argument
Parameters:
`x` - a Vector
Returns:
a new Vector
Throws:
`CardinalityException` - if the cardinalities differ
• #### normalize

`Vector normalize()`
Return a new vector containing the normalized (L_2 norm) values of the recipient
Returns:
a new Vector
• #### normalize

`Vector normalize(double power)`
Return a new Vector containing the normalized (L_power norm) values of the recipient.

See http://en.wikipedia.org/wiki/Lp_space

Technically, when `0 < power < 1`, we don't have a norm, just a metric, but we'll overload this here.

Also supports `power == 0` (number of non-zero elements) and power = `Double.POSITIVE_INFINITY` (max element). Again, see the Wikipedia page for more info

Parameters:
`power` - The power to use. Must be >= 0. May also be `Double.POSITIVE_INFINITY`. See the Wikipedia link for more on this.
Returns:
a new Vector x such that norm(x, power) == 1
• #### logNormalize

`Vector logNormalize()`
Return a new vector containing the log(1 + entry)/ L_2 norm values of the recipient
Returns:
a new Vector
• #### logNormalize

`Vector logNormalize(double power)`
Return a new Vector with a normalized value calculated as log_power(1 + entry)/ L_power norm.

Parameters:
`power` - The power to use. Must be > 1. Cannot be `Double.POSITIVE_INFINITY`.
Returns:
a new Vector
• #### norm

`double norm(double power)`
Return the k-norm of the vector.

See http://en.wikipedia.org/wiki/Lp_space

Technically, when `0 > power < 1`, we don't have a norm, just a metric, but we'll overload this here. Also supports power == 0 (number of non-zero elements) and power = `Double.POSITIVE_INFINITY` (max element). Again, see the Wikipedia page for more info.

Parameters:
`power` - The power to use.
`normalize(double)`
• #### minValue

`double minValue()`
Returns:
The minimum value in the Vector
• #### minValueIndex

`int minValueIndex()`
Returns:
The index of the minimum value
• #### maxValue

`double maxValue()`
Returns:
The maximum value in the Vector
• #### maxValueIndex

`int maxValueIndex()`
Returns:
The index of the maximum value
• #### plus

`Vector plus(double x)`
Return a new vector containing the sum of each value of the recipient and the argument
Parameters:
`x` - a double
Returns:
a new Vector
• #### plus

`Vector plus(Vector x)`
Return a new vector containing the element by element sum of the recipient and the argument
Parameters:
`x` - a Vector
Returns:
a new Vector
Throws:
`CardinalityException` - if the cardinalities differ
• #### set

```void set(int index,
double value)```
Set the value at the given index
Parameters:
`index` - an int index into the receiver
`value` - a double value to set
Throws:
`IndexException` - if the index is out of bounds
• #### setQuick

```void setQuick(int index,
double value)```
Set the value at the given index, without checking bounds
Parameters:
`index` - an int index into the receiver
`value` - a double value to set
• #### incrementQuick

```void incrementQuick(int index,
double increment)```
Increment the value at the given index by the given value.
Parameters:
`index` - an int index into the receiver
`increment` - sets the value at the given index to value + increment;
• #### getNumNondefaultElements

`int getNumNondefaultElements()`
Return the number of values in the recipient which are not the default value. For instance, for a sparse vector, this would be the number of non-zero values.
Returns:
an int
• #### getNumNonZeroElements

`int getNumNonZeroElements()`
Return the number of non zero elements in the vector.
Returns:
an int
• #### times

`Vector times(double x)`
Return a new vector containing the product of each value of the recipient and the argument
Parameters:
`x` - a double argument
Returns:
a new Vector
• #### times

`Vector times(Vector x)`
Return a new vector containing the element-wise product of the recipient and the argument
Parameters:
`x` - a Vector argument
Returns:
a new Vector
Throws:
`CardinalityException` - if the cardinalities differ
• #### viewPart

```Vector viewPart(int offset,
int length)```
Return a new vector containing the subset of the recipient
Parameters:
`offset` - an int offset into the receiver
`length` - the cardinality of the desired result
Returns:
a new Vector
Throws:
`CardinalityException` - if the length is greater than the cardinality of the receiver
`IndexException` - if the offset is negative or the offset+length is outside of the receiver
• #### zSum

`double zSum()`
Return the sum of all the elements of the receiver
Returns:
a double
• #### cross

`Matrix cross(Vector other)`
Return the cross product of the receiver and the other vector
Parameters:
`other` - another Vector
Returns:
a Matrix
• #### aggregate

```double aggregate(DoubleDoubleFunction aggregator,
DoubleFunction map)```
Examples speak louder than words: aggregate(plus, pow(2)) is another way to say getLengthSquared(), aggregate(max, abs) is norm(Double.POSITIVE_INFINITY). To sum all of the positive values, aggregate(plus, max(0)).
Parameters:
`aggregator` - used to combine the current value of the aggregation with the result of map.apply(nextValue)
`map` - a function to apply to each element of the vector in turn before passing to the aggregator
Returns:
the final aggregation
• #### aggregate

```double aggregate(Vector other,
DoubleDoubleFunction aggregator,
DoubleDoubleFunction combiner)```

Generalized inner product - take two vectors, iterate over them both, using the combiner to combine together (and possibly map in some way) each pair of values, which are then aggregated with the previous accumulated value in the combiner.

Example: dot(other) could be expressed as aggregate(other, Plus, Times), and kernelized inner products (which are symmetric on the indices) work similarly.

Parameters:
`other` - a vector to aggregate in combination with
`aggregator` - function we're aggregating with; fa
`combiner` - function we're combining with; fc
Returns:
the final aggregation; ```if r0 = fc(this[0], other[0]), ri = fa(r_{i-1}, fc(this[i], other[i])) for all i > 0```
• #### getLengthSquared

`double getLengthSquared()`
Return the sum of squares of all elements in the vector. Square root of this value is the length of the vector.
• #### getDistanceSquared

`double getDistanceSquared(Vector v)`
Get the square of the distance between this vector and the other vector.
• #### getLookupCost

`double getLookupCost()`
Gets an estimate of the cost (in number of operations) it takes to lookup a random element in this vector.
`double getIteratorAdvanceCost()`
`boolean isAddConstantTime()`