Texas Instruments TI-83 PLUS - Manual (Page 230)

TI-83 Plus Draw Instructions 227
patres specifies one of eight shading resolutions.
patres = 1 shades every pixel (default)
patres = 2 shades every second pixel
patres = 3 shades every third pixel
patres = 4 shades every fourth pixel
patres = 5 shades every fifth pixel
patres = 6 shades every sixth pixel
patres = 7 shades every seventh pixel
patres = 8 shades every eighth pixel
Shade( lowerfunc,upperfunc[,Xleft,Xright,pattern,patres] )