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Document DoubleVector #312

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136 changes: 133 additions & 3 deletions moa/src/main/java/moa/core/DoubleVector.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*
*/
package moa.core;

Expand All @@ -31,43 +31,88 @@ public class DoubleVector extends AbstractMOAObject {

private static final long serialVersionUID = 1L;

/** The underlying storage of the vector's values. */
protected double[] array;

/** Creates an empty DoubleVector. After creation, the length if this DoubleVector is 0. */
public DoubleVector() {
this.array = new double[0];
}

/**
* Creates an initialised DoubleVector. The values of the input array are copied into the new
* DoubleVector.
*
* @param toCopy the array to copy the numbers from
*/
public DoubleVector(double[] toCopy) {
this.array = new double[toCopy.length];
System.arraycopy(toCopy, 0, this.array, 0, toCopy.length);
}

/**
* Duplicates a DoubleVector. The values of the input DoubleVector are copied into the new
* object.
*
* @param toCopy the DoubleVector to copy the values from
*/
public DoubleVector(DoubleVector toCopy) {
this(toCopy.getArrayRef());
}

/**
* How long this DoubleVector is.
*
* @return the length of this DoubleVector
*/
public int numValues() {
return this.array.length;
}

/**
* Replaces the value at the specified position. If the DoubleVector is smaller than the
* required index, it grows to accommodate it.
*
* @param i the index of the value to replace
* @param v the number to store at the specified position
*/
public void setValue(int i, double v) {
if (i >= this.array.length) {
setArrayLength(i + 1);
}
this.array[i] = v;
}

/**
* Adds a number to one of the DoubleVector's values. If the position is greater than this
* DoubleVector's size, the vector grows to accommodate it and the number is inserted.
*
* @param i the position where to perform the operation
* @param v the number to add
*/
public void addToValue(int i, double v) {
if (i >= this.array.length) {
setArrayLength(i + 1);
}
this.array[i] += v;
}

/**
* Adds element-wise the values of a DoubleVector. If both vectors are not the same length, the
* shorter one behaves as if padded with zeros to match the longer one.
*
* @param toAdd a DoubleVector of numbers to add
*/
public void addValues(DoubleVector toAdd) {
addValues(toAdd.getArrayRef());
}

/**
* Adds element-wise the values of an array. If both containers are not the same length, the
* shorter one behaves as if padded with zeros to match the longer one.
*
* @param toAdd an array of numbers to add
*/
public void addValues(double[] toAdd) {
if (toAdd.length > this.array.length) {
setArrayLength(toAdd.length);
Expand All @@ -77,10 +122,22 @@ public void addValues(double[] toAdd) {
}
}

/**
* Subtracts element-wise the values of a DoubleVector. If both vectors are not the same length,
* the shorter one behaves as if padded with zeros to match the longer one.
*
* @param toSubtract a DoubleVector of numbers to subtract
*/
public void subtractValues(DoubleVector toSubtract) {
subtractValues(toSubtract.getArrayRef());
}

/**
* Subtracts element-wise the values of an array. If both containers are not the same length,
* the shorter one behaves as if padded with zeros to match the longer one.
*
* @param toSubtract an array of numbers to subtract
*/
public void subtractValues(double[] toSubtract) {
if (toSubtract.length > this.array.length) {
setArrayLength(toSubtract.length);
Expand All @@ -90,31 +147,57 @@ public void subtractValues(double[] toSubtract) {
}
}

/**
* Adds a number to all values of this DoubleVector.
*
* @param toAdd the number to add
*/
public void addToValues(double toAdd) {
for (int i = 0; i < this.array.length; i++) {
this.array[i] = this.array[i] + toAdd;
}
}

/**
* Multiplies all numbers in this DoubleVector by a factor.
*
* @param multiplier the factor to multiply by
*/
public void scaleValues(double multiplier) {
for (int i = 0; i < this.array.length; i++) {
this.array[i] = this.array[i] * multiplier;
}
}

// returns 0.0 for values outside of range
/**
* Returns the element at the specified position. Returns 0 for values outside of the range
* (index ≥ 0 || index &lt; numValues).
*
* @param i the index of the element to return
* @return the value at the specified index
*/
public double getValue(int i) {
return ((i >= 0) && (i < this.array.length)) ? this.array[i] : 0.0;
}

/**
* Sums the numbers in this DoubleVector.
*
* @return the addition of the values
*/
public double sumOfValues() {
double sum = 0.0;
for (double element : this.array) {
sum += element;
}
return sum;
}


/**
* Sums the magnitudes of the numbers in this DoubleVector.
*
* @return the addition of the absolute values
*/
public double sumOfAbsoluteValues() {
double sum = 0.0;
for (double element : this.array) {
Expand All @@ -123,6 +206,11 @@ public double sumOfAbsoluteValues() {
return sum;
}

/**
* Finds the position of the greatest number. If this DoubleVector is empty, returns -1.
*
* @return the position of the greatest value or -1
*/
public int maxIndex() {
int max = -1;
for (int i = 0; i < this.array.length; i++) {
Expand All @@ -133,10 +221,19 @@ public int maxIndex() {
return max;
}

/**
* Rescales the values to be between -1 and 1. The numbers in this DoubleVector are scaled so
* that the sum of their absolute values equals 1.
*/
public void normalize() {
scaleValues(1.0 / sumOfAbsoluteValues());
}

/**
* Counts the number of values different from zero.
*
* @return a count of values that are not 0
*/
public int numNonZeroEntries() {
int count = 0;
for (double element : this.array) {
Expand All @@ -147,6 +244,11 @@ public int numNonZeroEntries() {
return count;
}

/**
* Finds the smallest number in this DoubleVector.
*
* @return the smallest value of the DoubleVector. 0 if this DoubleVector is empty.
*/
public double minWeight() {
if (this.array.length > 0) {
double min = this.array[0];
Expand All @@ -160,16 +262,32 @@ public double minWeight() {
return 0.0;
}

/**
* Creates a copy of the underlying array of this DoubleVector.
*
* @return an array containing the values of this DoubleVector
*/
public double[] getArrayCopy() {
double[] aCopy = new double[this.array.length];
System.arraycopy(this.array, 0, aCopy, 0, this.array.length);
return aCopy;
}

/**
* Gives the underlying array of this DoubleVector.
*
* @return the array containing the values
*/
public double[] getArrayRef() {
return this.array;
}

/**
* Sets the size of the DoubleVector. If the new size is less than the current size, all values
* at index <code>l</code> and greater are discarded.
*
* @param l The new size of this DoubleVector. Must be positive.
*/
protected void setArrayLength(int l) {
double[] newArray = new double[l];
int numToCopy = this.array.length;
Expand All @@ -180,10 +298,22 @@ protected void setArrayLength(int l) {
this.array = newArray;
}

/**
* Represents the content of this DoubleVector.
*
* @param out the StringBuilder to build the representation in
*/
public void getSingleLineDescription(StringBuilder out) {
getSingleLineDescription(out, numValues());
}

/**
* Represents the <code>numValues</code> first entries in this DoubleVector. Padded with zeros
* at the end if it exceeds the length of this DoubleVector.
*
* @param out the StringBuilder to build the representation in
* @param numValues how many numbers to show
*/
public void getSingleLineDescription(StringBuilder out, int numValues) {
out.append("{");
for (int i = 0; i < numValues; i++) {
Expand Down