Here's a demo. I've chosen to use radians but you can use degrees with a few changes.
See inline comments for detail.
% For 12 months, compute 13 equally spaced angles where the
% first and last values will wrap to the same value.
theta = linspace(0,2*pi,13); % 12 equally spaced angles (13 points)
% Vector of radii values
r = randi(15,1,12); % 12 radii values
% Get month name abbreviations
monthNames = month(datetime(1, 1:12, 1), 's');
% Create polar plot
ax = polaraxes();
polarplot(ax, theta, r([1:end,1]), 'g-', 'LineWidth', 2)
% Set the polar axes units to radians, define the theta ticks
% and theta labels.
set(ax, 'ThetaAxisUnits', 'radians', 'ThetaTick', theta(1:end-1),...
'ThetaTickLabel', monthNames)
You can make further changes to the plot as needed suchs as putting January on top and making dotted reference lines. See polaraxes properties.
