DoubleMatrix1D
cern.colt.matrix.tdouble

Class DoubleMatrix1D

• All Implemented Interfaces:
Serializable, Cloneable
Direct Known Subclasses:
DenseDoubleMatrix1D, SparseDoubleMatrix1D, WrapperDoubleMatrix1D

```public abstract class DoubleMatrix1D
extends AbstractMatrix1D```
Abstract base class for 1-d matrices (aka vectors) holding double elements. First see the package summary and javadoc tree view to get the broad picture.

A matrix has a number of cells (its size), which are assigned upon instance construction. Elements are accessed via zero based indexes. Legal indexes are of the form [0..size()-1]. Any attempt to access an element at a coordinate index<0 || index>=size() will throw an IndexOutOfBoundsException.

Serialized Form
• Method Summary

Methods
Modifier and Type Method and Description
`double` ```aggregate(DoubleDoubleFunction aggr, DoubleFunction f)```
Applies a function to each cell and aggregates the results.
`double` ```aggregate(DoubleDoubleFunction aggr, DoubleFunction f, IntArrayList indexList)```
Applies a function to all cells with a given indexes and aggregates the results.
`double` ```aggregate(DoubleMatrix1D other, DoubleDoubleFunction aggr, DoubleDoubleFunction f)```
Applies a function to each corresponding cell of two matrices and aggregates the results.
`DoubleMatrix1D` `assign(double value)`
Sets all cells to the state specified by value.
`DoubleMatrix1D` `assign(double[] values)`
Sets all cells to the state specified by values.
`DoubleMatrix1D` `assign(DoubleFunction f)`
Assigns the result of a function to each cell; x[i] = function(x[i]).
`DoubleMatrix1D` `assign(DoubleMatrix1D other)`
Replaces all cell values of the receiver with the values of another matrix.
`DoubleMatrix1D` ```assign(DoubleMatrix1D y, DoubleDoubleFunction function)```
Assigns the result of a function to each cell; x[i] = function(x[i],y[i]).
`DoubleMatrix1D` ```assign(DoubleMatrix1D y, DoubleDoubleFunction function, IntArrayList nonZeroIndexes)```
Assigns the result of a function to each cell; x[i] = function(x[i],y[i]).
`DoubleMatrix1D` ```assign(DoubleProcedure cond, double value)```
Assigns a value to all cells that satisfy a condition.
`DoubleMatrix1D` ```assign(DoubleProcedure cond, DoubleFunction f)```
Assigns the result of a function to all cells that satisfy a condition.
`int` `cardinality()`
Returns the number of cells having non-zero values; ignores tolerance.
`DoubleMatrix1D` `copy()`
Constructs and returns a deep copy of the receiver.
`abstract Object` `elements()`
Returns the elements of this matrix.
`boolean` `equals(double value)`
Returns whether all cells are equal to the given value.
`boolean` `equals(Object obj)`
Compares this object against the specified object.
`double` `get(int index)`
Returns the matrix cell value at coordinate index.
`double[]` `getMaxLocation()`
Return the maximum value of this matrix together with its location
`double[]` `getMinLocation()`
Return the minimum value of this matrix together with its location
`void` ```getNegativeValues(IntArrayList indexList, DoubleArrayList valueList)```
Fills the coordinates and values of cells having negative values into the specified lists.
`void` ```getNonZeros(IntArrayList indexList, DoubleArrayList valueList)```
Fills the coordinates and values of cells having non-zero values into the specified lists.
`void` ```getNonZeros(IntArrayList indexList, DoubleArrayList valueList, int maxCardinality)```
Fills the coordinates and values of the first maxCardinality cells having non-zero values into the specified lists.
`void` ```getPositiveValues(IntArrayList indexList, DoubleArrayList valueList)```
Fills the coordinates and values of cells having positive values into the specified lists.
`abstract double` `getQuick(int index)`
Returns the matrix cell value at coordinate index.
`DoubleMatrix1D` `like()`
Construct and returns a new empty matrix of the same dynamic type as the receiver, having the same size.
`abstract DoubleMatrix1D` `like(int size)`
Construct and returns a new empty matrix of the same dynamic type as the receiver, having the specified size.
`abstract DoubleMatrix2D` ```like2D(int rows, int columns)```
Construct and returns a new 2-d matrix of the corresponding dynamic type, entirelly independent of the receiver.
`void` `normalize()`
Normalizes this matrix, i.e.
`abstract DoubleMatrix2D` ```reshape(int rows, int columns)```
Returns new DoubleMatrix2D of size rows x columns whose elements are taken column-wise from this matrix.
`abstract DoubleMatrix3D` ```reshape(int slices, int rows, int columns)```
Returns new DoubleMatrix3D of size slices x rows x columns, whose elements are taken column-wise from this matrix.
`void` ```set(int index, double value)```
Sets the matrix cell at coordinate index to the specified value.
`abstract void` ```setQuick(int index, double value)```
Sets the matrix cell at coordinate index to the specified value.
`void` `swap(DoubleMatrix1D other)`
Swaps each element this[i] with other[i].
`double[]` `toArray()`
Constructs and returns a 1-dimensional array containing the cell values.
`void` `toArray(double[] values)`
Fills the cell values into the specified 1-dimensional array.
`String` `toString()`
Returns a string representation using default formatting.
`DoubleMatrix1D` `viewFlip()`
Constructs and returns a new flip view.
`DoubleMatrix1D` ```viewPart(int index, int width)```
Constructs and returns a new sub-range view that is a width sub matrix starting at index.
`DoubleMatrix1D` `viewSelection(DoubleProcedure condition)`
Constructs and returns a new selection view that is a matrix holding the cells matching the given condition.
`DoubleMatrix1D` `viewSelection(int[] indexes)`
Constructs and returns a new selection view that is a matrix holding the indicated cells.
`DoubleMatrix1D` `viewSorted()`
Sorts the vector into ascending order, according to the natural ordering.
`DoubleMatrix1D` `viewStrides(int stride)`
Constructs and returns a new stride view which is a sub matrix consisting of every i-th cell.
`double` `zDotProduct(DoubleMatrix1D y)`
Returns the dot product of two vectors x and y, which is Sum(x[i]*y[i]).
`double` ```zDotProduct(DoubleMatrix1D y, int from, int length)```
Returns the dot product of two vectors x and y, which is Sum(x[i]*y[i]).
`double` ```zDotProduct(DoubleMatrix1D y, int from, int length, IntArrayList nonZeroIndexes)```
Returns the dot product of two vectors x and y, which is Sum(x[i]*y[i]).
`double` `zSum()`
Returns the sum of all cells; Sum( x[i] ).
• Methods inherited from class cern.colt.matrix.AbstractMatrix1D

`checkSize, index, size, stride, toStringShort`
• Methods inherited from class cern.colt.matrix.AbstractMatrix

`ensureCapacity, isView, trimToSize`
• Methods inherited from class cern.colt.PersistentObject

`clone`
• Methods inherited from class java.lang.Object

`getClass, hashCode, notify, notifyAll, wait, wait, wait`
• Method Detail

• aggregate

```public double aggregate(DoubleDoubleFunction aggr,
DoubleFunction f)```
Applies a function to each cell and aggregates the results. Returns a value v such that v==a(size()) where a(i) == aggr( a(i-1), f(get(i)) ) and terminators are a(1) == f(get(0)), a(0)==Double.NaN.

Example:

```         cern.jet.math.Functions F = cern.jet.math.Functions.functions;
matrix = 0 1 2 3

// Sum( x[i]*x[i] )
matrix.aggregate(F.plus,F.square);
--> 14

```
For further examples, see the package doc.
Parameters:
`aggr` - an aggregation function taking as first argument the current aggregation and as second argument the transformed current cell value.
`f` - a function transforming the current cell value.
Returns:
the aggregated measure.
`DoubleFunctions`
• aggregate

```public double aggregate(DoubleDoubleFunction aggr,
DoubleFunction f,
IntArrayList indexList)```
Applies a function to all cells with a given indexes and aggregates the results.
Parameters:
`aggr` - an aggregation function taking as first argument the current aggregation and as second argument the transformed current cell value.
`f` - a function transforming the current cell value.
`indexList` - indexes.
Returns:
the aggregated measure.
`DoubleFunctions`
• aggregate

```public double aggregate(DoubleMatrix1D other,
DoubleDoubleFunction aggr,
DoubleDoubleFunction f)```
Applies a function to each corresponding cell of two matrices and aggregates the results. Returns a value v such that v==a(size()) where a(i) == aggr( a(i-1), f(get(i),other.get(i)) ) and terminators are a(1) == f(get(0),other.get(0)), a(0)==Double.NaN.

Example:

```         cern.jet.math.Functions F = cern.jet.math.Functions.functions;
x = 0 1 2 3
y = 0 1 2 3

// Sum( x[i]*y[i] )
x.aggregate(y, F.plus, F.mult);
--> 14

// Sum( (x[i]+y[i])ˆ2 )
x.aggregate(y, F.plus, F.chain(F.square,F.plus));
--> 56

```
For further examples, see the package doc.
Parameters:
`aggr` - an aggregation function taking as first argument the current aggregation and as second argument the transformed current cell values.
`f` - a function transforming the current cell values.
Returns:
the aggregated measure.
Throws:
`IllegalArgumentException` - if size() != other.size().
`DoubleFunctions`
• assign

`public DoubleMatrix1D assign(DoubleFunction f)`
Assigns the result of a function to each cell; x[i] = function(x[i]). (Iterates downwards from [size()-1] to [0]).

Example:

```         // change each cell to its sine
matrix =   0.5      1.5      2.5       3.5
matrix.assign(cern.jet.math.Functions.sin);
-->
matrix ==  0.479426 0.997495 0.598472 -0.350783

```
For further examples, see the package doc.
Parameters:
`f` - a function object taking as argument the current cell's value.
Returns:
this (for convenience only).
`DoubleFunctions`
• assign

```public DoubleMatrix1D assign(DoubleProcedure cond,
DoubleFunction f)```
Assigns the result of a function to all cells that satisfy a condition.
Parameters:
`cond` - a condition.
`f` - a function object.
Returns:
this (for convenience only).
`DoubleFunctions`
• assign

```public DoubleMatrix1D assign(DoubleProcedure cond,
double value)```
Assigns a value to all cells that satisfy a condition.
Parameters:
`cond` - a condition.
`value` - a value.
Returns:
this (for convenience only).
• assign

`public DoubleMatrix1D assign(double value)`
Sets all cells to the state specified by value.
Parameters:
`value` - the value to be filled into the cells.
Returns:
this (for convenience only).
• assign

`public DoubleMatrix1D assign(double[] values)`
Sets all cells to the state specified by values. values is required to have the same number of cells as the receiver.

The values are copied. So subsequent changes in values are not reflected in the matrix, and vice-versa.

Parameters:
`values` - the values to be filled into the cells.
Returns:
this (for convenience only).
Throws:
`IllegalArgumentException` - if values.length != size().
• assign

`public DoubleMatrix1D assign(DoubleMatrix1D other)`
Replaces all cell values of the receiver with the values of another matrix. Both matrices must have the same size. If both matrices share the same cells (as is the case if they are views derived from the same matrix) and intersect in an ambiguous way, then replaces as if using an intermediate auxiliary deep copy of other.
Parameters:
`other` - the source matrix to copy from (may be identical to the receiver).
Returns:
this (for convenience only).
Throws:
`IllegalArgumentException` - if size() != other.size().
• assign

```public DoubleMatrix1D assign(DoubleMatrix1D y,
DoubleDoubleFunction function)```
Assigns the result of a function to each cell; x[i] = function(x[i],y[i]).

Example:

```         // assign x[i] = x[i]<sup>y[i]</sup>
m1 = 0 1 2 3;
m2 = 0 2 4 6;
m1.assign(m2, cern.jet.math.Functions.pow);
-->
m1 == 1 1 16 729

```
For further examples, see the package doc.
Parameters:
`y` - the secondary matrix to operate on.
`function` - a function object taking as first argument the current cell's value of this, and as second argument the current cell's value of y,
Returns:
this (for convenience only).
Throws:
`IllegalArgumentException` - if size() != y.size().
`DoubleFunctions`
• assign

```public DoubleMatrix1D assign(DoubleMatrix1D y,
DoubleDoubleFunction function,
IntArrayList nonZeroIndexes)```
Assigns the result of a function to each cell; x[i] = function(x[i],y[i]). (Iterates downwards from [size()-1] to [0]).

Example:

```         // assign x[i] = x[i]<sup>y[i]</sup>
m1 = 0 1 2 3;
m2 = 0 2 4 6;
m1.assign(m2, cern.jet.math.Functions.pow);
-->
m1 == 1 1 16 729

// for non-standard functions there is no shortcut:
m1.assign(m2,
new DoubleDoubleFunction() {
public double apply(double x, double y) { return Math.pow(x,y); }
}
);

```
For further examples, see the package doc.
Parameters:
`y` - the secondary matrix to operate on.
`function` - a function object taking as first argument the current cell's value of this, and as second argument the current cell's value of y.
`nonZeroIndexes` - list of indexes of non-zero values
Returns:
this (for convenience only).
Throws:
`IllegalArgumentException` - if size() != y.size().
`DoubleFunctions`
• cardinality

`public int cardinality()`
Returns the number of cells having non-zero values; ignores tolerance.
Returns:
the number of cells having non-zero values.
• copy

`public DoubleMatrix1D copy()`
Constructs and returns a deep copy of the receiver.

Note that the returned matrix is an independent deep copy. The returned matrix is not backed by this matrix, so changes in the returned matrix are not reflected in this matrix, and vice-versa.

Returns:
a deep copy of the receiver.
• elements

`public abstract Object elements()`
Returns the elements of this matrix.
Returns:
the elements
• equals

`public boolean equals(double value)`
Returns whether all cells are equal to the given value.
Parameters:
`value` - the value to test against.
Returns:
true if all cells are equal to the given value, false otherwise.
• equals

`public boolean equals(Object obj)`
Compares this object against the specified object. The result is `true` if and only if the argument is not `null` and is at least a `DoubleMatrix1D` object that has the same sizes as the receiver and has exactly the same values at the same indexes.
Overrides:
`equals` in class `Object`
Parameters:
`obj` - the object to compare with.
Returns:
`true` if the objects are the same; `false` otherwise.
• get

`public double get(int index)`
Returns the matrix cell value at coordinate index.
Parameters:
`index` - the index of the cell.
Returns:
the value of the specified cell.
Throws:
`IndexOutOfBoundsException` - if index<0 || index>=size().
• getMaxLocation

`public double[] getMaxLocation()`
Return the maximum value of this matrix together with its location
Returns:
{ maximum_value, location };
• getMinLocation

`public double[] getMinLocation()`
Return the minimum value of this matrix together with its location
Returns:
{ minimum_value, location };
• getNegativeValues

```public void getNegativeValues(IntArrayList indexList,
DoubleArrayList valueList)```
Fills the coordinates and values of cells having negative values into the specified lists. Fills into the lists, starting at index 0. After this call returns the specified lists all have a new size, the number of non-zero values.
Parameters:
`indexList` - the list to be filled with indexes, can have any size.
`valueList` - the list to be filled with values, can have any size.
• getNonZeros

```public void getNonZeros(IntArrayList indexList,
DoubleArrayList valueList)```
Fills the coordinates and values of cells having non-zero values into the specified lists. Fills into the lists, starting at index 0. After this call returns the specified lists all have a new size, the number of non-zero values.

In general, fill order is unspecified. This implementation fills like: for (index = 0..size()-1) do ... . However, subclasses are free to us any other order, even an order that may change over time as cell values are changed. (Of course, result lists indexes are guaranteed to correspond to the same cell).

Example:

```         0, 0, 8, 0, 7
-->
indexList  = (2,4)
valueList  = (8,7)

```
In other words, get(2)==8, get(4)==7.
Parameters:
`indexList` - the list to be filled with indexes, can have any size.
`valueList` - the list to be filled with values, can have any size.
• getNonZeros

```public void getNonZeros(IntArrayList indexList,
DoubleArrayList valueList,
int maxCardinality)```
Fills the coordinates and values of the first maxCardinality cells having non-zero values into the specified lists. Fills into the lists, starting at index 0. After this call returns the specified lists all have a new size, the number of non-zero values.

In general, fill order is unspecified. This implementation fills like: for (index = 0..size()-1) do ... . However, subclasses are free to us any other order, even an order that may change over time as cell values are changed. (Of course, result lists indexes are guaranteed to correspond to the same cell).

Example:

```         0, 0, 8, 0, 7
-->
indexList  = (2,4)
valueList  = (8,7)

```
In other words, get(2)==8, get(4)==7.
Parameters:
`indexList` - the list to be filled with indexes, can have any size.
`valueList` - the list to be filled with values, can have any size.
`maxCardinality` - maximal cardinality
• getPositiveValues

```public void getPositiveValues(IntArrayList indexList,
DoubleArrayList valueList)```
Fills the coordinates and values of cells having positive values into the specified lists. Fills into the lists, starting at index 0. After this call returns the specified lists all have a new size, the number of non-zero values.
Parameters:
`indexList` - the list to be filled with indexes, can have any size.
`valueList` - the list to be filled with values, can have any size.
• getQuick

`public abstract double getQuick(int index)`
Returns the matrix cell value at coordinate index.

Provided with invalid parameters this method may return invalid objects without throwing any exception. You should only use this method when you are absolutely sure that the coordinate is within bounds. Precondition (unchecked): index<0 || index>=size().

Parameters:
`index` - the index of the cell.
Returns:
the value of the specified cell.
• like

`public DoubleMatrix1D like()`
Construct and returns a new empty matrix of the same dynamic type as the receiver, having the same size. For example, if the receiver is an instance of type DenseDoubleMatrix1D the new matrix must also be of type DenseDoubleMatrix1D, if the receiver is an instance of type SparseDoubleMatrix1D the new matrix must also be of type SparseDoubleMatrix1D, etc. In general, the new matrix should have internal parametrization as similar as possible.
Returns:
a new empty matrix of the same dynamic type.
• like

`public abstract DoubleMatrix1D like(int size)`
Construct and returns a new empty matrix of the same dynamic type as the receiver, having the specified size. For example, if the receiver is an instance of type DenseDoubleMatrix1D the new matrix must also be of type DenseDoubleMatrix1D, if the receiver is an instance of type SparseDoubleMatrix1D the new matrix must also be of type SparseDoubleMatrix1D, etc. In general, the new matrix should have internal parametrization as similar as possible.
Parameters:
`size` - the number of cell the matrix shall have.
Returns:
a new empty matrix of the same dynamic type.
• like2D

```public abstract DoubleMatrix2D like2D(int rows,
int columns)```
Construct and returns a new 2-d matrix of the corresponding dynamic type, entirelly independent of the receiver. For example, if the receiver is an instance of type DenseDoubleMatrix1D the new matrix must be of type DenseDoubleMatrix2D, if the receiver is an instance of type SparseDoubleMatrix1D the new matrix must be of type SparseDoubleMatrix2D, etc.
Parameters:
`rows` - the number of rows the matrix shall have.
`columns` - the number of columns the matrix shall have.
Returns:
a new matrix of the corresponding dynamic type.
• normalize

`public void normalize()`
Normalizes this matrix, i.e. makes the sum of all elements equal to 1.0 If the matrix contains negative elements then all the values are shifted to ensure non-negativity.
• reshape

```public abstract DoubleMatrix2D reshape(int rows,
int columns)```
Returns new DoubleMatrix2D of size rows x columns whose elements are taken column-wise from this matrix.
Parameters:
`rows` - number of rows
`columns` - number of columns
Returns:
new 2D matrix with columns being the elements of this matrix.
• reshape

```public abstract DoubleMatrix3D reshape(int slices,
int rows,
int columns)```
Returns new DoubleMatrix3D of size slices x rows x columns, whose elements are taken column-wise from this matrix.
Parameters:
`rows` - number of rows
`columns` - number of columns
Returns:
new 2D matrix with columns being the elements of this matrix.
• set

```public void set(int index,
double value)```
Sets the matrix cell at coordinate index to the specified value.
Parameters:
`index` - the index of the cell.
`value` - the value to be filled into the specified cell.
Throws:
`IndexOutOfBoundsException` - if index<0 || index>=size().
• setQuick

```public abstract void setQuick(int index,
double value)```
Sets the matrix cell at coordinate index to the specified value.

Provided with invalid parameters this method may access illegal indexes without throwing any exception. You should only use this method when you are absolutely sure that the coordinate is within bounds. Precondition (unchecked): index<0 || index>=size().

Parameters:
`index` - the index of the cell.
`value` - the value to be filled into the specified cell.
• swap

`public void swap(DoubleMatrix1D other)`
Swaps each element this[i] with other[i].
Throws:
`IllegalArgumentException` - if size() != other.size().
• toArray

`public double[] toArray()`
Constructs and returns a 1-dimensional array containing the cell values. The values are copied. So subsequent changes in values are not reflected in the matrix, and vice-versa. The returned array values has the form
for (int i=0; i < size(); i++) values[i] = get(i);
Returns:
an array filled with the values of the cells.
• toArray

`public void toArray(double[] values)`
Fills the cell values into the specified 1-dimensional array. The values are copied. So subsequent changes in values are not reflected in the matrix, and vice-versa. After this call returns the array values has the form
for (int i=0; i < size(); i++) values[i] = get(i);
Throws:
`IllegalArgumentException` - if values.length < size().
• toString

`public String toString()`
Returns a string representation using default formatting.
Overrides:
`toString` in class `Object`
`DoubleFormatter`
• viewFlip

`public DoubleMatrix1D viewFlip()`
Constructs and returns a new flip view. What used to be index 0 is now index size()-1, ..., what used to be index size()-1 is now index 0. The returned view is backed by this matrix, so changes in the returned view are reflected in this matrix, and vice-versa.
Returns:
a new flip view.
• viewPart

```public DoubleMatrix1D viewPart(int index,
int width)```
Constructs and returns a new sub-range view that is a width sub matrix starting at index. Operations on the returned view can only be applied to the restricted range. Any attempt to access coordinates not contained in the view will throw an IndexOutOfBoundsException.

Note that the view is really just a range restriction: The returned matrix is backed by this matrix, so changes in the returned matrix are reflected in this matrix, and vice-versa.

The view contains the cells from index..index+width-1. and has view.size() == width. A view's legal coordinates are again zero based, as usual. In other words, legal coordinates of the view are 0 .. view.size()-1==width-1. As usual, any attempt to access a cell at other coordinates will throw an IndexOutOfBoundsException.

Parameters:
`index` - The index of the first cell.
`width` - The width of the range.
Returns:
the new view.
Throws:
`IndexOutOfBoundsException` - if index<0 || width<0 || index+width>size().
• viewSelection

`public DoubleMatrix1D viewSelection(DoubleProcedure condition)`
Constructs and returns a new selection view that is a matrix holding the cells matching the given condition. Applies the condition to each cell and takes only those cells where condition.apply(get(i)) yields true.

Example:

```         // extract and view all cells with even value
matrix = 0 1 2 3
matrix.viewSelection(
new DoubleProcedure() {
public final boolean apply(double a) { return a % 2 == 0; }
}
);
-->
matrix ==  0 2

```
For further examples, see the package doc. The returned view is backed by this matrix, so changes in the returned view are reflected in this matrix, and vice-versa.
Parameters:
`condition` - The condition to be matched.
Returns:
the new view.
• viewSelection

`public DoubleMatrix1D viewSelection(int[] indexes)`
Constructs and returns a new selection view that is a matrix holding the indicated cells. There holds view.size() == indexes.length and view.get(i) == this.get(indexes[i]). Indexes can occur multiple times and can be in arbitrary order.

Example:

```         this     = (0,0,8,0,7)
indexes  = (0,2,4,2)
-->
view     = (0,8,7,8)

```
Note that modifying indexes after this call has returned has no effect on the view. The returned view is backed by this matrix, so changes in the returned view are reflected in this matrix, and vice-versa.
Parameters:
`indexes` - The indexes of the cells that shall be visible in the new view. To indicate that all cells shall be visible, simply set this parameter to null.
Returns:
the new view.
Throws:
`IndexOutOfBoundsException` - if !(0 <= indexes[i] < size()) for any i=0..indexes.length()-1.
• viewSorted

`public DoubleMatrix1D viewSorted()`
Sorts the vector into ascending order, according to the natural ordering. This sort is guaranteed to be stable. For further information, see `DoubleSorting.sort(DoubleMatrix1D)`. For more advanced sorting functionality, see `DoubleSorting`.
Returns:
a new sorted vector (matrix) view.
• viewStrides

`public DoubleMatrix1D viewStrides(int stride)`
Constructs and returns a new stride view which is a sub matrix consisting of every i-th cell. More specifically, the view has size this.size()/stride holding cells this.get(i*stride) for all i = 0..size()/stride - 1.
Parameters:
`stride` - the step factor.
Returns:
the new view.
Throws:
`IndexOutOfBoundsException` - if stride <= 0.
• zDotProduct

`public double zDotProduct(DoubleMatrix1D y)`
Returns the dot product of two vectors x and y, which is Sum(x[i]*y[i]). Where x == this. Operates on cells at indexes 0 .. Math.min(size(),y.size()).
Parameters:
`y` - the second vector.
Returns:
the sum of products.
• zDotProduct

```public double zDotProduct(DoubleMatrix1D y,
int from,
int length)```
Returns the dot product of two vectors x and y, which is Sum(x[i]*y[i]). Where x == this. Operates on cells at indexes from .. Min(size(),y.size(),from+length)-1.
Parameters:
`y` - the second vector.
`from` - the first index to be considered.
`length` - the number of cells to be considered.
Returns:
the sum of products; zero if from<0 || length<0.
• zDotProduct

```public double zDotProduct(DoubleMatrix1D y,
int from,
int length,
IntArrayList nonZeroIndexes)```
Returns the dot product of two vectors x and y, which is Sum(x[i]*y[i]). Where x == this.
Parameters:
`y` - the second vector.
`nonZeroIndexes` - the indexes of cells in yhaving a non-zero value.
Returns:
the sum of products.
• zSum

`public double zSum()`
Returns the sum of all cells; Sum( x[i] ).
Returns:
the sum.