For matlab versions prior to 2016, you cannot adjust the tick intervals on polar plots but the current polar.m code has hard-coded intervals of 30deg. polarticks.m allows the user to adjust those intervals on previously established polar plots.

text_handles = polarticks (spokes, keep_lines, handle)
Where 'spokes' is the number of equally spaced ticks starting from 0deg (ie, 8 would create intervals of 45 deg, 10=36deg, 4=90deg etc) Must be an even integer.
'keep_lines' is a vector of line handles already plotted on the polar plot ([] if adjustments are done before plotting).

'handle' (optional) is the handle of the polar plot you are adjusting. ('gca' if not included).

The output 'text_handles' is a vector of handles of all ticklabels
Please contact me if any issues arise.

For more recent versions of matlab, use built-in functions polarplot() and thetaticks().
see: https://www.mathworks.com/help/matlab/creating_plots/polar-axes-grid-lines-and-labels.html