Thank you David for the links that are fun, informative and useful.
And thank you too Eddy for your reply. I appreciate that the extrema and centroid are two different things.
My question about the different calculations for the centroid's given by the Centroid and Show Extrema plugins remains.
For the curve track in Model Rail.cb (previously attached) the
Centroid plugin gives me a centroid position of -3.329323352, 187.688996172; while
Show Extrema plugin gives me a centroid position of -3.785, 185.309 which agrees with the position given by CamBam's Get Object Extremas tool (calculating the difference between extremas of x and y manually).
x = (-89.6030703701006+82.0337773860007)÷2 = −3.784646492
y = (211.99995943616−158.61856546735)÷2+158.61856546735 = 185.309262452
I am suggesting that the algorithm for calculating centroid in the Centroid plugin may be in error.
As I said, for my application the difference, (−0.4556 in x and 2.3797 in y), is not crucial but may be important for other situations.
Regards,
Paul
