Set two coefficients to be equal in lme()
Dear James,
Thank you for your answer. I have a follow-up question. In my `dat` dataset
below, "Treat" is coded {-.5, .5}. D1 & D2 are simply dummy coded {0, 1} .
My question is: why when I recode "Treat" as a factor {-.5="C", .5="T"},
then the model fails? Below is a reproducible example:
library(nlme)
(dat <- read.csv("https://raw.githubusercontent.com/hkil/m/master/mv.l.csv
"))
model_works <- lme(value ~ 0 + D1 + D2+D1:Treat+D2:Treat, random = ~0 + D1
+ D2 | Student, data = dat)
(dat2 <- transform(dat, Treat = ifelse(Treat==.5,"T", "C"))) # recode
Treat as a factor
model_fails <- lme(value ~ 0 + D1 + D2+D1:Treat+D2:Treat, random = ~0 + D1
+ D2 | Student, data = dat2)
On Sat, Jan 16, 2021 at 12:10 AM Uanhoro, James <
uanhoro.1 at buckeyemail.osu.edu> wrote:
Dear Simon,
Create a variable that is the sum of D1 * Treat and D2 * Treat and place
it in the model:
data$new_var <- (data$D1 + data$D2) * data$Treat
lme(value ~ 0 + D1 + D2 + new_var, random = ~0 + D1 + D2 | Student, data =
data)
The coefficient of new_var in the model above is the coefficient for both
variables if their coefficients were constrained equal.
James.
On Fri, 2021-01-15 at 23:42 -0600, Simon Harmel wrote:
Dear All,
I was wondering if it might be possible in my below model to set
"D1:Treat" and "D2:Treat" to be equal?
lme(value ~ 0 + D1 + D2 + D1:Treat + D2:Treat, random = ~0 + D1 + D2 |
Student, data = data)
Thank you,
Simon
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