An example of quartiles in code which creates the quartiles based on the DOLLARS field:
TABLE FILE ibisamp/ggsales
IN-GROUPS-OF 4 TILES
App Studio Report Canvas supports this too: Sort on the DOLLARS field, right-click it, and select Options.... In the pop-up window, select the Grouping tab and make your choices for the tiling you want.
I did not see any of these options in InfoAssist. I was able to get InfoAssist to produce quartiles by using hold files and computes. If you're interested, I can provide the code that InfoAssist generated for this.