java - How to calculate mean, median, mode and range from a set of numbers -

are there functions (as part of math library) calculate mean, median, mode , range set of numbers.

yes, there seem 3rd libraries (none in java math). 2 have come are:

http://opsresearch.com/app/

http://www.iro.umontreal.ca/~simardr/ssj/indexe.html

but, not difficult write own methods calculate mean, median, mode , range.

mean

public static double mean(double[] m) {     double sum = 0;     (int = 0; < m.length; i++) {         sum += m[i];     }     return sum / m.length; } 

median

// array double[] m must sorted public static double median(double[] m) {     int middle = m.length/2;     if (m.length%2 == 1) {         return m[middle];     } else {         return (m[middle-1] + m[middle]) / 2.0;     } } 

mode

public static int mode(int a[]) {     int maxvalue, maxcount;      (int = 0; < a.length; ++i) {         int count = 0;         (int j = 0; j < a.length; ++j) {             if (a[j] == a[i]) ++count;         }         if (count > maxcount) {             maxcount = count;             maxvalue = a[i];         }     }      return maxvalue; } 

---

update

as has been pointed out neelesh salpe, above not cater multi-modal collections. can fix quite easily:

public static list<integer> mode(final int[] numbers) {     final list<integer> modes = new arraylist<integer>();     final map<integer, integer> countmap = new hashmap<integer, integer>();      int max = -1;      (final int n : numbers) {         int count = 0;          if (countmap.containskey(n)) {             count = countmap.get(n) + 1;         } else {             count = 1;         }          countmap.put(n, count);          if (count > max) {             max = count;         }     }      (final map.entry<integer, integer> tuple : countmap.entryset()) {         if (tuple.getvalue() == max) {             modes.add(tuple.getkey());         }     }      return modes; } 

---

addition

if using java 8 or higher, can determine modes this:

public static list<integer> getmodes(final list<integer> numbers) {     final map<integer, long> countfrequencies = numbers.stream()             .collect(collectors.groupingby(function.identity(), collectors.counting()));      final long maxfrequency = countfrequencies.values().stream()             .maptolong(count -> count)             .max().orelse(-1);      return countfrequencies.entryset().stream()             .filter(tuple -> tuple.getvalue() == maxfrequency)             .map(map.entry::getkey)             .collect(collectors.tolist()); }