Bug: a88/8c9

Christian claims that Gary Acton has a script which does this, and
has asked for it. An algorithm for this is also described in the
Kirschvink paper.

Gary Acton has emailed me the code for this (in Fortran),
I think.

Also mentioned by GA in review comments on the paper:
‘For batch processing (like the many thousands of intervals measured along
U-channels), an automated PCA that recognizes and removes outliers would be
useful. That is the primary feature that ZPLOTIT has that PuffinPlot does not
and is the main reason I wrote ZPLOTIT. The outlier removing capability would
be easy to incorporate. In ZPLOTIT the user defines a minimum number of steps
to use in the PCA and a range of demagnetization steps over which to search.
If the range contains more than the minimum required steps, the program seeks
outlier steps, which are steps that degrade the PCA line fit significantly.
The PCA is then computed with and without outliers and the anchored and
unanchored PCA is provided for comparison. In PuffinPlot, one could
accomplish this but currently would have to do so for each individual sample,
which is not feasible when dealing with hundreds of meters of U-channels.’
This is presumably the algorithm implemented in the Fortran code,
and also looks similar (or possibly even identical) to the Kirschvink
algorithm.

Provisionally assigning to the ‘revised paper’ release, though
I may have to drop it if time runs out.

There won't be time to implement this for v1.01.