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Visualization of ranked likert-scale using advanced dot plot

I wish to produce a graph presenting responses to a number of agreement statements. The graph should allow for comparisons across the different groups of respondents and statement items.

I basically draw on a R code provided by Kastellec & Leoni (Figure 5; http://tables2graphs.com/doku.php?id=03_descriptive_statistics#figure_5).

In contrast to them, I would like to have the x-axis ranging from -5 to 5 and the table should be in the format of 2x2.

This code should produce sample data similar to the one I used:

mydata<-expand.grid(
col1=c('item1', 'item2', 'item3', 'item4'),
col2=c('0', '1', '3', '4'),
col3=c('T1', 'T2', 'C1', 'C2'))
mydata$col4=sapply(rnorm(64,0,1), function(x) {round(x,2)})

Note:
- col1: statement item („variable“ in the data set of K&L)
- col2: answer category ("period" in K&L)
- col3: group of respondent ("legislature" in K&L)
- col4: proportion ("proportion" in K&L)

And this is the code:

library(lattice)
    library(car)
 
    ltheme <- canonical.theme(color = FALSE) 
    ltheme$strip.background$col <- "lightgrey"  
    lattice.options(default.theme = ltheme)     
 
    mydata$col2<-factor(mydata$col2,
    levels=c(0,1,3,4),
    labels=c("strongly disagree", "disagree", "agree", "strongly agree"), ordered=TRUE)
 
    mydata$col3<-factor(mydata$col3,
    levels=c("T1", "C1", "T2", "C2"), ordered=TRUE)
    levels(mydata$col3)<-c("treatment group 1", "control group 1", "treatment group 2",  "control group 2")
 
    mydata$col1<-factor(mydata$col1,
    levels=c("item1", "item2", "item3", "item4"),
    labels=c("item 4", "item 3", "item 2", "item 1"), ordered=TRUE)
 
    prop.vec<-c(-5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5)
 
    plot<-dotplot(mydata$col1~mydata$col4|mydata$col3, xlab="levels of agreement",
    data=mydata,
    groups=mydata$col2,
    layout=c(2,2),
    scales=list(cex=0.65,
    x=list(at=prop.vec),
    alternating=3),
    par.strip.text=list(lines=2.5,cex=0.65),
    panel=function(...){
       panel.abline(v=prop.vec, col="lightgrey")
       panel.abline(h=1:11, col="lightgrey", lty=2)
       panel.xyplot(...)},
    as.table=TRUE,
    par.settings=simpleTheme(pch=c(19,1,2,17), cex=0.7), 
    auto.key=list(space="bottom", column=4, cex=0.65)
    )
 
    trellis.device(file="figure.pdf", device="pdf", color=FALSE, width=6, height=8)
 
    print(plot, newpage=FALSE)              
 
    dev.off()