[Boost-users] [accumulators] "count" NaN but otherwise ignore it?

Is there a feature within accumulators to count NaNs on extraction but to otherwise ignore them? Maybe some sort of pass filter on incoming data? I've got a situation where I'd like to avoid NaNs clobbering otherwise useful information, but I still want to total count of data seen to include them. The context is a time integrator for a physics simulation. The integrator tracks the number of timesteps. When the physics kicks back a NaN (because something's amiss), I'd like to count the failed timestep but not have the NaN destroy the useful mean of timesteps taken thus far. Thanks, Rhys