Question

我正在编写一个子例程来返回纵向混合效果模型的输出。我希望能够将变量列表中的元素作为结果变量和预测变量传递到lme/lmer中。我还希望能够在这些混合效果模型中指定对比度，但是我很难让contrasts()参数将字符串识别为同一{{中的模型规范中引用的变量名1}}通话。

这里有一些玩具数据，

lme/lme4

现在，在指定对比度的情况下，对set.seed(345) A0 <- rnorm(4,2,.5) B0 <- rnorm(4,2+3,.5) A1 <- rnorm(4,6,.5) B1 <- rnorm(4,6+2,.5) A2 <- rnorm(4,10,.5) B2 <- rnorm(4,10+1,.5) A3 <- rnorm(4,14,.5) B3 <- rnorm(4,14+0,.5) score <- c(A0,B0,A1,B1,A2,B2,A3,B3) id <- rep(1:8,times = 4, length = 32) time <- factor(rep(0:3, each = 8, length = 32)) group <- factor(rep(c("A","B"), times =2, each = 4, length = 32)) df <- data.frame(id = id, group = group, time = time, score = score)的以下调用就可以正常工作（我知道这些是默认的，所以这纯粹是教学目的）。

lme

以下内容也可以使用mod <- lme(score ~ group*time, random = ~1|id, data = df, contrasts = list(group = contr.treatment(2), time = contr.treatment(4)))函数将字符串作为变量名传递到lme中。

reformulate()

但是，如果我想指定对比度，就像第一个示例一样，那是行不通的

t <- "time"
g <- "group"
dv <- "score"

mod1R <- lme(reformulate(paste0(g,"*",t), response = "score"), random = ~1|id, data = df)

我如何获得mod2R <- lme(reformulate(paste0(g,"*",t), response = "score"), random = ~1|id, data = df, contrasts = list(g = contr.treatment(2), t = contr.treatment(4))) # Error in `contrasts<-`(`*tmp*`, value = contrasts[[i]]) : contrasts apply only to factors来认识到lme参数中指定的字符串是指传递给contrasts函数的变量？

Answer 1

您应该能够在对比列表上使用setNames()来将全名应用到列表中：

# Using a %>% pipe so need to load magrittr
library(magrittr)

mod2R <- lme(reformulate(paste0(g,"*",t), response = "score"), 
             random = ~1|id, 
             data = df, 
             contrasts = list(g = contr.treatment(2), t = contr.treatment(4)) %>%
                 setNames(c(g, t))
             )

将字符串传递到lme / lmer

1 个答案: