cuonglm answer solves your typo, to get the values in ascending order (as asked in your comment), pipe the output through sort -n -k 2 (sort as numbers (-n, on second field (-k 2), after changing the print statement to output the floats as in your example:

$ ps -A --sort -rss -o comm,pmem | awk '
  NR == 1 { print; next }
  { a[$1] += $2 }
  END {
    for (i in a) {
      printf "%-15s\t%.1f\n", i, a[i];
    }
  }
' | sed 's/%MEM/-1MEM/' | sort -n -k 2 | sed 's/-1MEM/%MEM/'


Output (using your table as input instead of doing ps on my system):

COMMAND         %MEM
evince          1.3
hud-service     1.5
nautilus        1.8
skype           2.2
Xorg            2.3
atom            4.4
compiz          4.8
chrome          11.6
firefox         28.2


Alternatively you can pipe the output through this python program (if you want descending sort (as in your example), change the reverse=False into reverse=True:


#! /usr/bin/env python
# coding: utf-8

import sys
import operator

d = {}
for line in sys.stdin:
    try:
        name, val = line.split()
        val = float(val)
        d.setdefault(name, [0.0])[0] += val
    except ValueError:
        print line,

for x in sorted(d.items(), reverse=False, key=operator.itemgetter(1)):
    print "{:16s}{:&gt;4}".format(x[0], x[1][0])


awk - Group by and sum column values
In two previous questions, it was clearly agreed that hesitating before playing a singleton specifically, and hesitating during play as a bluff generally constitute "wrongful/unethical hesitation." As an advanced beginner, I don't understand this rule at all.

I know that at the highest level, the best way to play and not give away any information about your holding to the opponents is to play each card at a nice even tempo. I am not a world class player; I am not even an advanced player (if I endplay you, I promise it wasn't intentional). As such, I frequently need to pause and calculate what to play, even in situations where the correct play should be obvious. 

Knowing that I will inevitably need to pause and consider a play and that that pause will provide my opponents with the information that I had a potentially difficult decision to make, why is it considered unethical for me to occasionally insert a similar pause before a routine play?

It isn't as if I could use such a pause to reliably signal something to my partner. In fact, this strategy removes the temptation for partner to draw unauthorized inferences from my pauses.
