Second-moments

In the MeasureObjectSizeShape module, it says:

My math/geometry is a little rusty. What exactly is the second-moment of the region? Is there a reference source for this kind of stuff?

Thanks.

Hi Scott,

It may be helpful to think of it in terms of analogy to statistics: the 1st moment is the mean, and the 2nd moment is the variance around the mean. In physics, the 1st moment is the centroid, and the 2nd moment describes the tendency of an region to twist around a given axis. Expressing a shape into a rectangle with the same moments is standard practice in structural engineering/design link].

It took some doing to find a simple reference (Wikipedia’s entry seemed a bit too technical), but I found this one at eHow.

Hope this helps!
-Mark

Hello,
I’ve got a similar question regarding the ‘orientation’ measurement, e.g. what exactly is the angle reported? I’m analysing the orientation of nuclei as my objects, and assumed that it’d be an angle of the longer axis of the ellipse fit in my object, but when i use ‘display data on image’ module that doesn’t seem right.
Thank you,