What's the metric of the eccentricity parameter in xy_grid() function?
I have programmed an experiment in which a set of objects is presented in a circle using the xy_grid() function and eccentricity is manipulated by varying the 'rho' parameter. However, based on the online documentation alone I cannot tell what kind of distance metric is this parameter using (ie., milimeters, degrees, etc). I would appreciate if you could clarify this question to me.
Thank you in advance.