Do you want to draw bar charts or dials on your LCD screens? Don't write the code, steal mine. This code includes 3 functions, a vertical bar chart, a horizontal bar chart, and a dial. These functions work with Arduino UNO or MEGA, and an Adafruit 3.5 inch 320 x 480 LDC display. This code may work with other displays that use the Adafruit_GFX libraries.
Usage video https://www.youtube.com/watch?v=U5hOU-xxQgk
Arduino INO code with the graphing functions (from my personal pcloud account). Note: I tried to include the code but it exceeded the 9000 character limit http://pc.cd/EWirtalK
Link to the Adafruit LCD display and libraries https://learn.adafruit.com/adafruit-3-5-color-320x480-tft-touchscreen-breakout/overview