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Re: [Phys-l] independent variables, or not



On Fri, Jan 13, 2012 at 11:05 AM, John Denker <jsd@av8n.com> wrote:

On 01/13/2012 11:07 AM, LaMontagne, Bob wrote:

Unless you have deliberate control over the choice of one of the
variables, I don't really see where dependency and independency enter
the choice of axes. I simply state to my students that the expression
"plot A vs B" has a standard interpretation of A on the vertical axes
and B on the horizontal.

Amen, brother.


Yet another issue to keep in mind if you are doing a curve fit:

Most curve fitting routines make the explicit assumption that the
uncertainty in the horizontal axis quantities is much smaller than the
uncertainty in the vertical axis quantities. If your particular data set
violates that assumption, you might want to swap horizontal and vertical
before fitting--never mind which variable is under your control.

John

--
John E Gastineau
Staff Scientist and Partner
Vernier Software & Technology