@Carl Love This question has arisen a few times: How to get the effect of a smooth curve (ie. adequate number of points, preferably using default adaptive plotting) and only a modest number of symbols overlaid.
The option style=pointline ties the number of symbols to the generated data points, unfortunately. Hence these solutions to forcibly overlay two "plots" -- one for the curve with adaptive plotting and one for the symbols at a modest number of points without adaptive plotting.
It might be useful for it to be automatically available, so that people don't have to figure out the overlaid scheme as suggested. Also, the forced overlay results in additional data in the constructed plot structure, and that might make external export of the data more fiddly.
Perhaps this kind of thing would be a better (and more commonly desired) result from the style=pointline option itself? Is the current behaviour really more desirable? If so could it benefit from some option modification so as to specify the number of rendered symbols separately from the specification of the number of curve data points? And how about requesting their spacing evenly by arclength rather than by value of the independent parameter? Comments?