使用nmle包

Question

我正在使用nlme包来学习多级模型，并遵循教科书中的示例＆＃34;使用R＆＃34发现统计数据;当它发生时。

Mixed Models Code

数据集是蜜月Period.dat，也可以在其配套网站下载。

Data Set - Multilevel Models

require(nlme)
require(reshape2)
satisfactionData = read.delim("Honeymoon Period.dat",  header = TRUE)

restructuredData<-melt(satisfactionData, id = c("Person", "Gender"), measured = c("Satisfaction_Base", "Satisfaction_6_Months", "Satisfaction_12_Months", "Satisfaction_18_Months"))
names(restructuredData)<-c("Person", "Gender", "Time", "Life_Satisfaction")


#print(restructuredData)
#restructuredData.sorted<-restructuredData[order(Person),]

intercept <-gls(Life_Satisfaction~1, data = restructuredData, method = "ML", na.action = na.exclude)
randomIntercept <-lme(Life_Satisfaction ~1, data = restructuredData, random = ~1|Person, method = "ML",  na.action = na.exclude, control = list(opt="optim"))
anova(intercept, randomIntercept)

timeRI<-update(randomIntercept, .~. + Time)
timeRS<-update(timeRI, random = ~Time|Person)
ARModel<-update(timeRS, correlation = corAR1(0, form = ~Time|Person))

此时出现错误，当我尝试更新＆＃34; timeRS＆＃34;模型。 错误消息如下：

  

as.character.factor（X [[i]]，...）出错：格式错误的因素

这里的任何统计人员/程序员都知道这意味着什么？

Answer 1

我看过这本书。似乎编码是错误的。你得到的错误是因为你的时间变量是一个因素，你需要它是数字。在作者的第一个图中，他将时间表示为数字（0 - 3），但他的模型代码不正确。我已经为你记录了它：

## First, Time needs to be recoded as a numeric

restructuredData$Time.Numeric <- with(restructuredData, ifelse(Time == "Satisfaction_Base", 0, 
        ifelse(Time == "Satisfaction_6_Months", 1,
        ifelse(Time == "Satisfaction_12_Months", 2,
        ifelse(Time == "Satisfaction_18_Months", 3, NA)))))

## Baseline Model

intercept <-gls(Life_Satisfaction~1, data = restructuredData, method = "ML", na.action = na.exclude)

summary(intercept)

## Model where intercept can vary for Individuals

randomIntercept <- lme(Life_Satisfaction ~ 1, data = restructuredData, random = ~1|Person, method = "ML", na.action = na.exclude, control = list(opt = "optim"))

summary(randomIntercept)

## Add time as a fixed effect

timeRI <- lme(Life_Satisfaction ~ Time.Numeric, data = restructuredData, random = ~1|Person, method = "ML", na.action = na.exclude, control = list(opt = "optim"))

summary(timeRI)

## Add a random slope to the model by nesting the Individual within the test time

timeRS <- lme(Life_Satisfaction ~ Time.Numeric, data = restructuredData, random = ~Time.Numeric|Person, method = "ML", na.action = na.exclude, control = list(opt = "optim"))

summary(timeRS)


## Modeling the covariance structure structure of the errors with a first-order autoregressive covariance structure

ARModel <- update(timeRS, correlation = corAR1(0, form = ~Time.Numeric|Person))

summary(ARModel)

anova(intercept, randomIntercept, timeRI, timeRS, ARModel)

anova读出的模型比较现在完全如书中所示。