In reply to Barry.

Yes, but be careful when you look at charts that have reference lines. It is easy to misinterpret them to mean that a curve doubles in 2-3 days if it lies between the 2-day and 3-day reference lines. That is NOT a correct interpretation! You need to estimate the slope at the END of a curve and compare it to the reference lines. I've seen more recent plots that use the color of the line to represent the estimate of doubling time, which is probably easier for nonexperts to understand.