This is a script that will change the resolution in Linux on a Macbook Pro Retina computer. Nvidia-current is required for the script to function properly. Tested in Ubuntu 13.04 (alpha).

Res.sh

#!/bin/bash
#Author:  Travis Gibson
#This script requires an argument for the resolution width
#Thanks go out to eCharles for a patch in the comments of this link here: http://blog.echarles.net/2013/10/01/Ubuntu-13.04-On-MacbookPro-Retina
if [ -z "$1" ]; then
	echo "Usage: Res.sh <resolution_width>";
	exit 1;
fi
erg=$( echo "$1")
check=$(xrandr -q | grep DP-2 | cut -d " " -f 4 | cut -d "x" -f 1)
if [ "$erg" -eq  "$check" ]; then
	echo "The screen is already at this resolution"
	exit 1;	
fi

resolution=$(xrandr -q | grep DP-2 | cut -d " " -f 3);

if [ "$resolution" != "2880x1800+0+0" ]; then 
	xrandr --output DP-2 --scale 1x1;
#Necessary to work around an issue where re-scaling 
#only works if the scale is set to 1x1
	sleep 3;
fi
scale_w=$(echo "scale=4; $1/2880" | bc; exit );
arg=$(echo "$scale_w""x""$scale_w")
xrandr --output DP-2 --scale $arg
sleep 1;

I'm completely new when it comes to Ubuntu, or linux in general. How do you run this script?

@Avilis In Terminal, navigate to this file and type "sh Res.sh"

Thanks for sharing this script.
I adapted this script to automatically detect the screen resolution and make the correct adjustments based on those values (https://gist.github.com/npcardoso/ff937ebca6fc0a80ea3d).
I only tested it in a MBP 11,1 so let me know if it does not work for you.

I have macbook pro retina haswell 13' and this code doesn't work for my machine. How can I fix this problem ? Please help me !

Thanks for sharing. I modified it to automatically discover the adapter's name. In my case the adapter's name was "VGA-0" and not "DP-2" as I am running Ubuntu 14.04.02 on VirtualBox on MacBook Pro 15'.
https://gist.github.com/Viperus-/0c87ce21cbfef24c30a2
Tested only in MacBookPro11,2.