Question on NFWPhaesSpace. about halotools HOT 2 CLOSED

Thanks for catching this @kgb0255. Your example does seem to indicate a problem with this function - I'll take a look ASAP and try out your proposed fix when I do.

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Hi @kgb0255 my apologies for letting this issue get forgotten. But I'm now turning attention to a new release of halotools, and so I've been spending some time this morning sorting through the sign convention issue you raised. I think this may just be due to a misunderstanding of the definition of the sign convention adopted by halotools when defining relative velocities.

Consider the example you gave:

For example, if x1=1, x2=2, v1=1, v2=0, the relative position of particle 1 with respect to particle 2 should be -1, and the relative velocity should be 1

In this example, the particles are moving towards each other, and so their relative velocity should be negative, as returned by halotools, not positive. That convention is explained in this line of the docstring. Does this clarify the issue?

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