st: z-score diff plots

[Nikos Kakouros <nkakouros@gmail.com>]

Dear StataList,

I'd like to first apologize upfront for the lack of specificity in my
question - please be sensitive to my lack of experience with Stata. :)

I have two tests that are meant to measure the same thing (blood
thickness) but with totally different units. On the whole they
correlate well (patients with thick blood have higher values on both
measurements), but the first test is affected (on univariate analysis)
by another blood parameter but the second test is not. Their
correlation is, therefore, dependent on the third parameter.

I would appreciate on comments/advice on how to best visually show
this relationship in Stata. I was thinking the following: convert all
measurements to z-scores and depict the difference in z-score for the
two measurements at different values (y axis) vs the value of the
third variable that affects one of the tests more than the other
(x-axis).

Is anyone familiar with such a visualization?

Thanking you in advance,

Nikos
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