Hello all,
As I read through the "Doing meta in R" website and to the part of
meta-regression, this is the example that the website provides in order to
change the categorical moderators into numerical ones (since you need
"numbers" to begin to test the interaction between moderators):
--------------------------------------------------------------------
# Add factor labels to 'continent'
# 0 = Europe
# 1 = North America
levels(MVRegressionData$continent) = c("Europe", "North America")
--------------------------------------------------------------------
and I thought of my own data. I have a moderator in my data named "Duration
of treatment," with "Short", "Medium", "Long" and "N/A"(some of the studies
didn't provide the duration of treatment). In this case, how would I code
in order to change this moderator into numerical order to begin the
meta-regression analysis?
Nick
??? (Nick Chen)
Email: t571 at wlgsh.tp.edu.tw <t5741 at wlgsh.tp.edu.tw>
[R-meta] About meta-regression analysis
2 messages · 英文科陳品誠, Wolfgang Viechtbauer
Dear Nick, One does not have to manually change a categorical moderator into a numerical one to examine interactions. Of course, categorical moderators are represented in a model in terms of numerical variables (typically via a set of dummy variables), but R can handle all of this encoding for you automatically. Here is an example with two categorical variables, one consisting of two levels, the other with three levels: https://www.metafor-project.org/doku.php/tips:multiple_factors_interactions Best, Wolfgang
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Sent: Monday, December 11, 2023 08:38
To: r-sig-meta-analysis at r-project.org
Cc: ?????? <t571 at wlgsh.tp.edu.tw>
Subject: [R-meta] About meta-regression analysis
Hello all,
As I read through the "Doing meta in R" website and to the part of
meta-regression, this is the example that the website provides in order to
change the categorical moderators into numerical ones (since you need
"numbers" to begin to test the interaction between moderators):
--------------------------------------------------------------------
# Add factor labels to 'continent'
# 0 = Europe
# 1 = North America
levels(MVRegressionData$continent) = c("Europe", "North America")
--------------------------------------------------------------------
and I thought of my own data. I have a moderator in my data named "Duration
of treatment," with "Short", "Medium", "Long" and "N/A"(some of the studies
didn't provide the duration of treatment). In this case, how would I code
in order to change this moderator into numerical order to begin the
meta-regression analysis?
Nick
??? (Nick Chen)
Email: t571 at wlgsh.tp.edu.tw <t5741 at wlgsh.tp.edu.tw>