Averages/Median

Averages/Median
You are encouraged to solve this task according to the task description, using any language you may know.

Write a program to find the median value of a vector of floating-point numbers. The program need not handle the case where the vector is empty, but must handle the case where there are an even number of elements.

See also: Mean

Java

Works with: Java version 1.5+

<lang java5>public static double median(List<Double> list){

  Collections.sort(list);
  if(list.size() % 2 == 0){
     return (list.get((list.size()) / 2) + list.get((list.size()) / 2 - 1)) / 2;
  }
  return list.get((list.size()-1)/2);

}</lang>

Ruby

<lang ruby>def median(ary)

 return nil if ary.empty?
 mid, rem = ary.length.divmod(2)
 if rem == 0
   ary.sort[mid-1,2].inject(:+) / 2.0
 else
   ary.sort[mid]
 end

end

p median([]) # => nil p median([5,3,4]) # => 4 p median([5,4,2,3]) # => 3.5 p median([3,4,1,-8.4,7.2,4,1,1.2]) # => 2.1</lang>

Tcl

<lang tcl>proc median args {

   set list [lsort -real $args]
   set len [llength $list]
   # Odd number of elements
   if {$len & 1} {
       return [lindex $list [expr {($len-1)/2}]]
   }
   # Even number of elements
   set idx2 [expr {$len/2}]
   set idx1 [expr {$idx2-1}]
   return [expr {
       ([lindex $list $idx1] + [lindex $list $idx2])/2.0
   }]

}

puts [median 3.0 4.0 1.0 -8.4 7.2 4.0 1.0 1.2]; # --> 2.1</lang>