schizophrenia {mixor} | R Documentation |
In the NIMH Schizophrenia Collaborative Study, patients were randomized to receive one of four medications, either placebo or one of three different anti-psychotic drugs. The protocol indicated subjects were to then be evaluated at weeks 0, 1, 3, 6 to assess severity of illness; additionally some measurements were made at weeks 2, 4, and 5.
data(schizophrenia)
A data frame with 1603 observations on the following 9 variables.
id
a numeric vector indicating the unique patient identifier
imps79
a numeric vector from item 79 on the Inpatient Multidimensional Psychiatric Scale indicating severity of illness. The scores were applied to be interpreted as follows: 1 = normal, not ill at all; 2 = borderline mentally ill; 3 = mildly ill; 4 = moderately ill; 5 = markedly ill; 6 = severly ill; 7 = among the most extremely ill
imps79b
a binary version of imps79
imps79o
an ordinally scaled version of imps79
int
a numeric vector of ones; used in stand-alone package to indicate intercept
TxDrug
a numeric vector indicating treatment with drug (1) or placebo (0)
Week
a numeric vector indicating time, in weeks
SqrtWeek
the square root of the Week variable
TxSWeek
a variable representing the TxDrug x Week interaction
From http://tigger.uic.edu/~hedeker/SCHIZX1.DAT.txt
Hedeker D. and Gibbons R.D. (1996) A computer program for mixed-effects ordinal regression analysis. Computer Methods and Programs in Biomedicine 49, 157-176. Hedeker D and Gibbons R.D. (2006) Longitudinal Data Analysis, Wiley, Hoboken, New Jesery.
library("mixor") data("schizophrenia") ### Random intercept SCHIZO1.fit<-mixor(imps79o ~ TxDrug + SqrtWeek + TxSWeek, data=schizophrenia, id=id, link="probit") summary(SCHIZO1.fit) ### Random intercept and slope SCHIZO2.fit<-mixor(imps79o ~ TxDrug + SqrtWeek + TxSWeek, data=schizophrenia, id=id, which.random.slope=2, link="probit") summary(SCHIZO2.fit) # random intercept and trend with independent random effects; using logit link SCHIZO3.fit<-mixor(imps79o ~ TxDrug + SqrtWeek + TxSWeek, data=schizophrenia, id=id, which.random.slope=2, indep.re=TRUE, link="logit") summary(SCHIZO3.fit)