Notes inline...
On 11/24/2015 08:28 AM, Gilles wrote:
On Tue, 24 Nov 2015 06:52:04 -0700, Phil Steitz wrote:
I need the following methods to complete the fix for MATH-1246. I
can add them as private methods to the KS class; but they seem
generally useful, so I propose adding them to MathArrays. Any
objections?
/**
* Concatenates two arrays.
*
* @param x first array
* @param y second array
* @return a new array consisting of the entries of x followed by
the entries of y
* @throws NullPointerException if either x or y is null
*/
public static double[] concat(double[] x, double[] y)
I'd propose
public static double[] cat(double[] ... arrays)
Java 8 has an addAll method that is similar to the cat method:
http://docs.oracle.com/javase/8/docs/api/java/util/ArrayList.html#addAll-int-java.util.Collection-
Perhaps use a similar naming convention...
The cat API is also does what Javascript's splice method does, so that might be
a better name.
http://www.w3schools.com/jsref/jsref_splice.asp
/**
* Returns an array consisting of the unique values in {@code data}.
* The return array is sorted in descending order.
*
* @param data
* @return descending list of values included in the input array
*/
public static double[] values(double[] data)
I'd suggest
public static double[] uniq(double[] data)
Just a note - Java 8 Streams make the implementation fairly short:
|Integer[]array =newInteger[]{5,10,20,58,10};Stream.of(array).distinct().forEach(i
->System.out.print(" "+i)); 5, 10, 20, 58 //Printed |
Cheers,
- Ole
/**
* Adds random jitter to {@code data} using deviates sampled from
{@code dist}.
* <p>
* Note that jitter is applied in-place - i.e., the array
* values are overwritten with the result of applying jitter.</p>
*
* @param data input/output data array
* @param dist probability distribution to sample for jitter values
* @throws NullPointerException if either of the parameters is null
*/
public static void jitter(double[] data, RealDistribution dist)
IMO, this method should be part of the new API proposed in
https://issues.apache.org/jira/browse/MATH-1158
Like so:
/** {@inheritDoc} */
public RealDistribution.Sampler createSampler(final RandomGenerator rng) {
return new RealDistribution.Sampler() {
public double next() { /* ... */ }
public double[] next(int sampleSize) { /* ... */ }
/**
* @param data input/output data array.
* @param dist probability distribution to sample for jitter values
* @throws NullPointerException if data array is null.
*/
public void jitter(double[] data) {
final int len = data.length;
final double[] jit = next(len);
for (int i = 0; i < len; i++) {
data[i] += jit[i];
}
}
};
}
Advantages:
* Simpler to use (half as many arguments). :-)
* Utility is defined where the base functionality is defined.
* Avoid adding to the overcrowded MathArrays utility class.
* Avoid dependency to another package (will help with modularization).
Drawbacks from usage POV
* None (?)
Drawbacks from implementation POV
* Cannot be done before we agree to go forward with the aforementioned issue.
In the meantime, I suggest to implement it as a "private" method.
Regards,
Gilles
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