Unable to set a Default Resolution in i3

I have a 4k monitor screen on laptop and the default configuration makes the icons very small to work with. I changed the resolution to 1920x1080 using xrandr. I got to know this step can be automated creating monitor.sh using arandr. I followed the steps and uncommented the line in the config file as well. But this is not working. Whenever i reboot/logout the machine i need to manually run the monitor.sh to correct the resolution. Can you guys please help me?