qyaxis(x0, [y0 y1], yy) plots an y-axis with ticks at yy. (yy may be empty.)
qyaxis(x0, yy) calculates y0 and y1 from yy.
qyaxis(x0, [], yy) only draws ticks, not an axis line.
qyaxis(..., lbls) where lbls is either a cell array or numeric vector the same size as yy overrides the default tick labels. Labels are suppressed if lbls is empty.
qyaxis(..., ttl) adds a title to the axis.

qyaxis obeys settings from qticklen, qtextdist, and qaxshift.
qyaxis('r', ...) inverts the sign of these settings.
qyaxis('R', ...) additionally orients the title the other way.

Either lbls or yy (but not both) may be a function handle in which case the labels are calculated from the tick positions (or vice versa). For example:
     qyaxis(0, [0:0.2:1], @(y) (y*100), 'Value (%)')

Without any arguments or with just a title as an argument, qyaxis tries to determine sensible defaults based on previous calls to qplot. Your mileage may vary.