Intersections [R for BE/BA]

posted by Helmut Homepage – Vienna, Austria, 2017-10-31 12:32 (1498 d 23:06 ago) – Posting: # 17958
Views: 20,292

Hi Astea,

» Now everything became clear excepting directly intersections. If the calculation of TimeLow and TimeDur are based on the difference between intersections, why are they not included into output or elsewhere?

Ask Certara. ;-)
If there is no demand by customers it will not be implemented. Even if there is one, it may take ages. Example: The intercept of the log/linear-regression used in the estimation of λz was only part of the Core output (if Intermediate Output was selected) up to release 7.0… Since the EMA stated “by Cmin,ss we mean the concentration at the end of the dosage interval, i.e. Ctrough in 2010 it took seven years to get both Cmin (as in previous versions) and Ctau (observed if t=τ or predicted if t≠τ) in the output and the option to compute concentrations at arbitrary times (useful for Cτ in SD). Before we needed a workaround.

» Of course, the structure of the curve should be more complicated and there could be several intersections...

Exactly. See here, there, and my example above.

» So, how to get pointed values 0.595 to 8.386 or 0.595 to 8.257 not by hand, brain, R, Excel but by Phoenix?

IMHO, in Phoenix/WinNonlin impossible. In Phoenix/NLME doable since PML (Phoenix Modeling Language) offers the required features to loop through the data.
May I ask: Why do you need the intersections? Curiosity (aka “nice to know”)?

» For a single peak chart I come up with insane ideas of initial data manipulation namely truncating or reflecting the curve.

Nice try! As you rightly observed: Does not work for multiple intersections and/or >1 subject.

Dif-tor heh smusma 🖖
Helmut Schütz
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