> print(mean(N[-burn.in]))
[1] 50.50544
> print(mean(P[1,-burn.in]))
[1] 0.6147702
> print(mean(P[2,-burn.in]))
[1] 0.1851454
> print(mean(Y[1,-burn.in]))
[1] 31.18056
> print(mean(Y[2,-burn.in]))
[1] 9.256889
> print(median(N[-burn.in]))
[1] 50
> print(median(P[1,-burn.in]))
[1] 0.6327573
> print(median(P[2,-burn.in]))
[1] 0.1471702
> print(median(Y[1,-burn.in]))
[1] 31
> print(median(Y[2,-burn.in]))
[1] 7
> print(var(N[-burn.in]))
[1] 51.3479
> print(var(P[1,-burn.in]))
[1] 0.03901431
> print(var(P[2,-burn.in]))
[1] 0.02246281
> print(var(Y[1,-burn.in]))
[1] 137.611
> print(var(Y[2,-burn.in]))
[1] 65.51218
We can see from the above statistics that the mean is slightly higher than the median for P_2 and Y_2 implying they are skewed to the left. 
The variance of Y and N is larger than P of course, but interestingly N is more stable than each of the Y's