[R-meta] Fwd: Coding for length of time in longitudinal studies given its use in meta-regression

[Farzad Keyhan]

Dear All (sending again in case my data didn't show correctly),

My collaborators and I want to code for the "length of time" (`length`)
elapsed between the last treatment and each post-test in each of our
longitudinal studies (an example is below).

My question is that since `length` is a moderator that only applies to
"post-tests" and NOT to the "pre-tests", is it correct (i.e., from the
perspective of using `length` in meta-regression) to put "0" for all
 "pre-test" rows (up to row # 18)?

Note that "0" is a meaningful value for `length`. For example, in the study
coded below, "post-test 1" (i.e., time == 1) has an actual `length` of "0".

Thank you for your assistance,
Fred
     study         mT      sdT  nT     mC      sdC nC  group  length time
13   xxx    67.590 19.260 17 51.900 28.320 20         1       0    0
14   xxx    67.590 19.260 17 51.900 28.320 20         1       0    0
15   xxx    53.110 21.730 18 51.900 28.320 20         2       0    0
16   xxx    53.110 21.730 18 51.900 28.320 20         2       0    0
17   xxx    59.350 18.390 20 51.900 28.320 20         3       0    0
18   xxx    59.350 18.390 20 51.900 28.320 20         3       0    0
19   xxx    82.530 14.330 17 52.750 23.260 20         1       0    1
20   xxx    77.500 16.070 18 52.750 23.260 20         2       0    1
21   xxx    81.250 13.000 20 52.750 23.260 20         3       0    1
22   xxx    82.650 15.470 17 63.900 18.890 20         1       7    2
23   xxx    76.780 20.670 18 63.900 18.890 20         2       7    2
24   xxx    80.050 12.090 20 63.900 18.890 20         3       7    2

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