Arrays (Starjava TTOOLS API)

java.lang.Object
- uk.ac.starlink.ttools.func.Arrays

```
public class Arrays
extends java.lang.Object
```
Functions which operate on array-valued cells. The array parameters of these functions can only be used on values which are already arrays (usually, numeric arrays). In most cases that means on values in table columns which are declared as array-valued. FITS and VOTable tables can have columns which contain array values, but other formats such as CSV cannot.
If you want to calculate aggregating functions like sum, min, max etc on multiple values which are not part of an array, it's easier to use the functions from the Lists class.
Note that none of these functions will calculate statistical functions over a whole column of a table.
The functions fall into a number of categories:
- Aggregating operations, which map an array value to a scalar, including size, count, countTrue, maximum, minimum, sum, mean, median, quantile, stdev, variance, join.
- Operations on one or more arrays which produce array results, including add, subtract, multiply, divide, reciprocal, condition, slice, pick. Mostly these work on any numeric array type and return floating point (double precision) values, but some of them (slice, pick) have variants for different array types.
- The function array, which lets you assemble a floating point array value from a list of scalar numbers. There are variants (intArray, stringArray) for some different array types.
Since:

14 Jul 2008

Author:

Mark Taylor

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method	Description
`static double[]`	`add(java.lang.Object array, double constant)`	Returns the result of adding a constant value to every element of a numeric array.
`static double[]`	`add(java.lang.Object array1, java.lang.Object array2)`	Returns the result of adding two numeric arrays element by element.
`static double[]`	`array(double... values)`	Returns a floating point numeric array built from the given arguments.
`static double[]`	`condition(boolean[] flagArray, double trueValue, double falseValue)`	Maps a boolean array to a numeric array by using supplied numeric values to represent true and false values from the input array.
`static int`	`count(java.lang.Object array)`	Returns the number of non-blank elements in the array.
`static int`	`countTrue(boolean[] array)`	Returns the number of true elements in an array of boolean values.
`static double[]`	`divide(java.lang.Object array1, java.lang.Object array2)`	Returns the result of dividing two numeric arrays element by element.
`static int[]`	`intArray(int... values)`	Returns an integer numeric array built from the given arguments.
`static java.lang.String`	`join(java.lang.Object array, java.lang.String joiner)`	Returns a string composed of concatenating all the elements of an array, separated by a joiner string.
`static double`	`maximum(java.lang.Object array)`	Returns the largest of the non-blank elements in the array.
`static double`	`mean(java.lang.Object array)`	Returns the mean of all the non-blank elements in the array.
`static double`	`median(java.lang.Object array)`	Returns the median of the non-blank elements in the array.
`static double`	`minimum(java.lang.Object array)`	Returns the smallest of the non-blank elements in the array.
`static double[]`	`multiply(java.lang.Object array, double constant)`	Returns the result of multiplying every element of a numeric array by a constant value.
`static double[]`	`multiply(java.lang.Object array1, java.lang.Object array2)`	Returns the result of multiplying two numeric arrays element by element.
`static byte[]`	`pick(byte[] array, int... indices)`
`static double[]`	`pick(double[] array, int... indices)`	Returns a selection of elements from a given array.
`static float[]`	`pick(float[] array, int... indices)`
`static int[]`	`pick(int[] array, int... indices)`
`static long[]`	`pick(long[] array, int... indices)`
`static short[]`	`pick(short[] array, int... indices)`
`static java.lang.Object[]`	`pick(java.lang.Object[] array, int... indices)`
`static java.lang.String[]`	`pick(java.lang.String[] array, int... indices)`
`static double`	`quantile(java.lang.Object array, double quant)`	Returns a quantile value of the non-blank elements in the array.
`static double[]`	`reciprocal(java.lang.Object array)`	Returns the result of taking the reciprocal of every element of a numeric array.
`static int`	`size(java.lang.Object array)`	Returns the number of elements in the array.
`static byte[]`	`slice(byte[] array, int i0, int i1)`
`static double[]`	`slice(double[] array, int i0, int i1)`	Returns a sub-sequence of values from a given array.
`static float[]`	`slice(float[] array, int i0, int i1)`
`static int[]`	`slice(int[] array, int i0, int i1)`
`static long[]`	`slice(long[] array, int i0, int i1)`
`static short[]`	`slice(short[] array, int i0, int i1)`
`static java.lang.Object[]`	`slice(java.lang.Object[] array, int i0, int i1)`
`static java.lang.String[]`	`slice(java.lang.String[] array, int i0, int i1)`
`static double`	`stdev(java.lang.Object array)`	Returns the population standard deviation of all the non-blank elements in the array.
`static java.lang.String[]`	`stringArray(java.lang.String... values)`	Returns a String array built from the given arguments.
`static double[]`	`subtract(java.lang.Object array1, java.lang.Object array2)`	Returns the result of subtracting one numeric array from the other element by element.
`static double`	`sum(java.lang.Object array)`	Returns the sum of all the non-blank elements in the array.
`static double`	`variance(java.lang.Object array)`	Returns the population variance of all the non-blank elements in the array.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Method Detail
  - sum
```
public static double sum(java.lang.Object array)
```
    Returns the sum of all the non-blank elements in the array. If array is not a numeric array, null is returned.
    
    Parameters:
    
    array - array of numbers
    
    Returns:
    
    sum of all the numeric values in array
  - mean
```
public static double mean(java.lang.Object array)
```
    Returns the mean of all the non-blank elements in the array. If array is not a numeric array, null is returned.
    
    Parameters:
    
    array - array of numbers
    
    Returns:
    
    mean of all the numeric values in array
  - variance
```
public static double variance(java.lang.Object array)
```
    Returns the population variance of all the non-blank elements in the array. If array is not a numeric array, null is returned.
    
    Parameters:
    
    array - array of numbers
    
    Returns:
    
    variance of the numeric values in array
  - stdev
```
public static double stdev(java.lang.Object array)
```
    Returns the population standard deviation of all the non-blank elements in the array. If array is not a numeric array, null is returned.
    
    Parameters:
    
    array - array of numbers
    
    Returns:
    
    standard deviation of the numeric values in array
  - minimum
```
public static double minimum(java.lang.Object array)
```
    Returns the smallest of the non-blank elements in the array. If array is not a numeric array, null is returned.
    
    Parameters:
    
    array - array of numbers
    
    Returns:
    
    minimum of the numeric values in array
  - maximum
```
public static double maximum(java.lang.Object array)
```
    Returns the largest of the non-blank elements in the array. If array is not a numeric array, null is returned.
    
    Parameters:
    
    array - array of numbers
    
    Returns:
    
    maximum of the numeric values in array
  - median
```
public static double median(java.lang.Object array)
```
    Returns the median of the non-blank elements in the array. If array is not a numeric array, null is returned.
    
    Parameters:
    
    array - array of numbers
    
    Returns:
    
    median of the numeric values in array
  - quantile
```
public static double quantile(java.lang.Object array,
                              double quant)
```
    Returns a quantile value of the non-blank elements in the array. Which quantile is determined by the quant value; values of 0, 0.5 and 1 give the minimum, median and maximum respectively. A value of 0.99 would give the 99th percentile.
    
    Parameters:
    
    array - array of numbers
    
    quant - number in the range 0-1 deterining which quantile to calculate
    
    Returns:
    
    quantile corresponding to quant
  - size
```
public static int size(java.lang.Object array)
```
    Returns the number of elements in the array. If array is not an array, zero is returned.
    
    Parameters:
    
    array - array
    
    Returns:
    
    size of array
  - count
```
public static int count(java.lang.Object array)
```
    Returns the number of non-blank elements in the array. If array is not an array, zero is returned.
    
    Parameters:
    
    array - array (may or may not be numeric)
    
    Returns:
    
    number of non-blank elements in array
  - countTrue
```
public static int countTrue(boolean[] array)
```
    Returns the number of true elements in an array of boolean values.
    
    Parameters:
    
    array - array of true/false values
    
    Returns:
    
    number of true values in array
  - join
```
public static java.lang.String join(java.lang.Object array,
                                    java.lang.String joiner)
```
    Returns a string composed of concatenating all the elements of an array, separated by a joiner string. If array is not an array, null is returned.
    
    Parameters:
    
    array - array of numbers or strings
    
    joiner - text string to interpose between adjacent elements
    
    Returns:
    
    string composed of array elements separated by joiner strings
    
    Examples:
    
    join(array(1.5,2.1,-3.9), "; ") = "1.5; 2.1; -3.9"
  - add
```
public static double[] add(java.lang.Object array1,
                           java.lang.Object array2)
```
    Returns the result of adding two numeric arrays element by element. Both arrays must be numeric, and the arrays must have the same length. If either of those conditions is not true, null is returned. The types of the arrays do not need to be the same, so for example it is permitted to add an integer array to a floating point array.
    
    Parameters:
    
    array1 - first array of numeric values
    
    array2 - second array of numeric values
    
    Returns:
    
    element-by-element sum of array1 and array2, the same length as the input arrays
    
    Examples:
    
    add(array(1,2,3), array(0.1,0.2,0.3)) = [1.1, 2.2, 3.3]
  - add
```
public static double[] add(java.lang.Object array,
                           double constant)
```
    Returns the result of adding a constant value to every element of a numeric array. If the supplied array argument is not a numeric array, null is returned.
    
    Parameters:
    
    array - array input
    
    constant - value to add to each array element
    
    Returns:
    
    array output, the same length as the array parameter
    
    Examples:
    
    add(array(1,2,3), 10) = [11,12,13]
  - subtract
```
public static double[] subtract(java.lang.Object array1,
                                java.lang.Object array2)
```
    Returns the result of subtracting one numeric array from the other element by element. Both arrays must be numeric, and the arrays must have the same length. If either of those conditions is not true, null is returned. The types of the arrays do not need to be the same, so for example it is permitted to subtract an integer array from a floating point array.
    
    Parameters:
    
    array1 - first array of numeric values
    
    array2 - second array of numeric values
    
    Returns:
    
    element-by-element difference of array1 and array2, the same length as the input arrays
    
    Examples:
    
    subtract(array(1,2,3), array(0.1,0.2,0.3)) = [0.9, 1.8, 2.7]
  - multiply
```
public static double[] multiply(java.lang.Object array1,
                                java.lang.Object array2)
```
    Returns the result of multiplying two numeric arrays element by element. Both arrays must be numeric, and the arrays must have the same length. If either of those conditions is not true, null is returned. The types of the arrays do not need to be the same, so for example it is permitted to multiply an integer array by a floating point array.
    
    Parameters:
    
    array1 - first array of numeric values
    
    array2 - second array of numeric values
    
    Returns:
    
    element-by-element product of array1 and array2, the same length as the input arrays
    
    Examples:
    
    multiply(array(1,2,3), array(2,4,6)) = [2, 8, 18]
  - multiply
```
public static double[] multiply(java.lang.Object array,
                                double constant)
```
    Returns the result of multiplying every element of a numeric array by a constant value. If the supplied array argument is not a numeric array, null is returned.
    
    Parameters:
    
    array - array input
    
    constant - value by which to multiply each array element
    
    Returns:
    
    array output, the same length as the array parameter
    
    Examples:
    
    multiply(array(1,2,3), 2) = [2, 4, 6]
  - divide
```
public static double[] divide(java.lang.Object array1,
                              java.lang.Object array2)
```
    Returns the result of dividing two numeric arrays element by element. Both arrays must be numeric, and the arrays must have the same length. If either of those conditions is not true, null is returned. The types of the arrays do not need to be the same, so for example it is permitted to divide an integer array by a floating point array.
    
    Parameters:
    
    array1 - array of numerator values (numeric)
    
    array2 - array of denominator values (numeric)
    
    Returns:
    
    element-by-element result of array1[i]/array2[i] the same length as the input arrays
    
    Examples:
    
    divide(array(0,9,4), array(1,3,8)) = [0, 3, 0.5]
  - reciprocal
```
public static double[] reciprocal(java.lang.Object array)
```
    Returns the result of taking the reciprocal of every element of a numeric array. If the supplied array argument is not a numeric array, null is returned.
    
    Parameters:
    
    array - array input
    
    Returns:
    
    array output, the same length as the array parameter
    
    Examples:
    
    reciprocal(array(1,2,0.25) = [1, 0.5, 4]
  - condition
```
public static double[] condition(boolean[] flagArray,
                                 double trueValue,
                                 double falseValue)
```
    Maps a boolean array to a numeric array by using supplied numeric values to represent true and false values from the input array.
    This has the same effect as applying the expression outArray[i] = flagArray[i] ? trueValue : falseValue.
    
    Parameters:
    
    flagArray - array of boolean values
    
    trueValue - output value corresponding to an input true value
    
    falseValue - output value corresponding to an input false value
    
    Returns:
    
    output numeric array, same length as flagArray
    
    Examples:
    
    condition([true, false, true], 1, 0) = [1, 0, 1]
  - slice
```
public static double[] slice(double[] array,
                             int i0,
                             int i1)
```
    Returns a sub-sequence of values from a given array.
    The semantics are like python array slicing, though both limits have to be specified: the output array contains the sequence of elements in the input array from i0 (inclusive) to i1 (exclusive). If a negative value is given in either case, it is added to the length of the input array, so that -1 indicates the last element of the input array. The indices are capped at 0 and the input array length respectively, so a large positive value may be used to indicate the end of the array. If the end index is less than or equal to the start index, a zero-length array is returned.
    Note: This documents the double-precision version of the routine. Corresponding routines exist for other data types (float, long, int, short, byte, String, Object).
    
    Parameters:
    
    array - input array
    
    i0 - index of first element, inclusive (may be negative to count back from the end)
    
    i1 - index of the last element, exclusive (may be negative to count back from the end)
    
    Returns:
    
    array giving the sequence of elements specified by i0 and i1
    
    Examples:
    
    slice(array(10,11,12,13), 0, 3) = [10, 11, 12], slice(array(10,11,12,13), -2, 999) = [12, 13]
  - slice
```
@HideDoc
public static float[] slice(float[] array,
                            int i0,
                            int i1)
```
  - slice
```
@HideDoc
public static long[] slice(long[] array,
                           int i0,
                           int i1)
```
  - slice
```
@HideDoc
public static int[] slice(int[] array,
                          int i0,
                          int i1)
```
  - slice
```
@HideDoc
public static short[] slice(short[] array,
                            int i0,
                            int i1)
```
  - slice
```
@HideDoc
public static byte[] slice(byte[] array,
                           int i0,
                           int i1)
```
  - slice
```
@HideDoc
public static java.lang.String[] slice(java.lang.String[] array,
                                       int i0,
                                       int i1)
```
  - slice
```
@HideDoc
public static java.lang.Object[] slice(java.lang.Object[] array,
                                       int i0,
                                       int i1)
```
  - pick
```
public static double[] pick(double[] array,
                            int... indices)
```
    Returns a selection of elements from a given array.
    The output array consists of one element selected from the input array for each of the supplied index values. If a negative value is supplied for an index value, it is added to the input array length, so that -1 indicates the last element of the input array. If the input array is null, null is returned. If any of the index values is out of the range of the extent of the input array, an error results.
    Note: This documents the double-precision version of the routine. Corresponding routines exist for other data types (float, long, int, short, byte, String, Object).
    
    Parameters:
    
    array - input array
    
    indices - one or more index into the input array (may be negative to count back from the end)
    
    Returns:
    
    array giving the elements specified by indices
    
    Examples:
    
    pick(array(10,11,12,13), 0, 3) = [10, 13], pick(array(10,11,12,13), -1, -2, -3) = [13, 12, 11]
  - pick
```
@HideDoc
public static float[] pick(float[] array,
                           int... indices)
```
  - pick
```
@HideDoc
public static long[] pick(long[] array,
                          int... indices)
```
  - pick
```
@HideDoc
public static int[] pick(int[] array,
                         int... indices)
```
  - pick
```
@HideDoc
public static short[] pick(short[] array,
                           int... indices)
```
  - pick
```
@HideDoc
public static byte[] pick(byte[] array,
                          int... indices)
```
  - pick
```
@HideDoc
public static java.lang.String[] pick(java.lang.String[] array,
                                      int... indices)
```
  - pick
```
@HideDoc
public static java.lang.Object[] pick(java.lang.Object[] array,
                                      int... indices)
```
  - array
```
public static double[] array(double... values)
```
    Returns a floating point numeric array built from the given arguments.
    
    Parameters:
    
    values - one or more array elements
    
    Returns:
    
    array
  - intArray
```
public static int[] intArray(int... values)
```
    Returns an integer numeric array built from the given arguments.
    
    Parameters:
    
    values - one or more array elements
    
    Returns:
    
    array
  - stringArray
```
public static java.lang.String[] stringArray(java.lang.String... values)
```
    Returns a String array built from the given arguments.
    
    Parameters:
    
    values - one or more array elements
    
    Returns:
    
    array

Class Arrays

Method Summary

Methods inherited from class java.lang.Object

Method Detail

sum

mean

variance

stdev

minimum

maximum

median

quantile

size

count

countTrue

join

add

add

subtract

multiply

multiply

divide

reciprocal

condition

slice

slice

slice

slice

slice

slice

slice

slice

pick

pick

pick

pick

pick

pick

pick

pick

array

intArray

stringArray