Runs the counter and user screen when collecting activity data. Called by analysis_pet(). Calls weigh_one_sample(), clean_list(), pet_analysis_done(), and pet_analysis_scale(). This function operates the user screen when the operator is using the counter. The first argument is a flag that should be true if the function has been called from pet_analysis_scale(), and false otherwise. This flag serves to keep the stack from exploding out of proportion when switching back and forth between pet_analysis_scale() and pet_analysis_counter(). When a switch is required, the function chooses between calling pet_analysis_scale(), or returning to it.