How to find the bin at which the smooth curve on an histogram passes through before it smoothens out

I computed a smoothing on a histogram by using the function provided here. Is there a way to automatically compute or find the last bin the curve passes through before it smoothens outs. For better explanation of what am trying to achieve, consider the histogram below.

How can I find the bin (rectangle marked with the straight line) without having to look at the histogram?? which is 0.5 for the first histogram and 0.4 for the second. Can I automatically get those values??