Calculate the median values for a set of groups.


median takes the first blank space-separated column
values and the remainder as keys. It will then print
the median for each key. As a side effect median will
will print the result sorted by the keys.

Usage example:

$ cat <<EOF | median
+003  c
.001  a
-002  b
+001  c
-001  b
+002  c
EOF
.001  a
-001.5  b
+002  c