[seqfan] Re: Chewing an old bone
davidwwilson at comcast.net
Tue Oct 25 05:31:37 CEST 2011
On 10/24/2011 8:21 PM, David Applegate wrote:
>> I really hope that the qlog plot will remain *supplementary* to the
>> log plot (for large signed sequences), and will not replace it. Each
>> of these plots can be the more useful one depending on applications.
> Do you have an example of when plotting log(|a(n)|+1) or
> log(a(n)+1) is more informative than plotting qlog(a(n))?
> David Applegate
- For positive n, a qlog(n) plot retains all of the visual information
of a log(|n|+1) plot.
- qlog(n) is odd and monotonically increasing, hence order and sign
preserving. In a
qlog(n) plot, positive values lie above the x-axis, negative below.
trend upward, decreasing downward. None of this is true of the
- For all positive n, qlog(n) is closer to the holy grail, log(n), than
- Admittedly, the qlog(n) scale is not a standard plotting scale, but
then, neither is
the log(|n|+1) scale. Apart from the OEIS, what other source uses the
Is it a builtin in any graphing package?
For these reasons, the qlog(n) scale is the equal or superior of the
log(|n|+1) in every
respect. To answer David Applegate's question, there is no information
in a log(|n|+1)
plot that is not better represented in a qlog(n) plot. Indeed, this was
my motivation for
constructing the qlog(n) scale in the first place: to address the
deficits of the log(|n|+1)
scale in regard to plotting negative values, while retaining its virtues
with regard to
plotting large ranges (and by sheer luck, qlog(n) happens to be closer
The new scale was intended to supplant the old, not to supplement it. If
the qlog(n) scale, the log(|a(n)|+1) scale becomes superfluous and can
be safely retired.
There would be no technical reason to keep it, and its weakness with
regard to plotting
negative values would argue to retire it.
In the end I suppose it is NJAS's decision. I hope he reads this mail.
More information about the SeqFan