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These are Posts that have been published by DJKeenan

Recently, I published the following paper.

"Calibration of a radiocarbon age", Nonlinear Processes in Geophysics, 19: 345–350 (2012).

The paper explains that all radiocarbon dates are inaccurate, due to an error in the handling of the statistics.

The paper has a Supplement, which includes a program to do the statistics correctly:

At present, there seems to be no way to generate a plot and then export it under program control. One solution to this, which could be implemented in under an hour, is a new command plottools:-export. This would provide a program interface to the functionality that is currently available by right-clicking on a plot and then selecting “Export”. Relatedly, a simple way to get a plot into ImageTools (and to do this under program control) would enhance Maple's graphics capabilities. The cost/benefit ratio for this seems to be extremely strong.
I was writing a small procedure to generate random points on the unit sphere. The details are not directly relevant here, but the procedure was as follows.
randspherepts := proc(n::nonnegint, d::posint) 
 local i, p, r; 
 description "Returns co-ords of n random pts on the d-dimensional unit sphere [Knuth, 1998: sect. 3.4.1E]"; 
 uses ArrayTools;
 p:= Matrix(n, d, RandomTools:-Generate('distribution(Normal(0,1))', makeproc=true),datatype='hfloat',order='C_order');
 r:= ElementPower(AddAlongDimension(ElementPower(p,2),2),1/2);  
 seq(ElementDivide(p[i,1..-1],r[i]), i=1..n) 
end proc;
I was recently asked what I thought of using Approximate Entropy in financial trading. I was not much familiar with ApEn; so I experimented a little. A natural thing to do is consider long bit strings that are suspected of being able to (but not known to) pass general tests for randomness. Examples include leading bits of Pi, sqrt(2), etc. So I began with the following. PiFive:=evalf[350000](Pi): bits:=convert(PiFive,binary,1000000): (Such things are helpful in various applications, not just studying ApEn.)
It is easy to not notice that there is new mail in my inbox. How about a more prominent notice, when the inbox is non-empty?—e.g. something like the boxed notice that appears at the top when I earn new points?
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