plot Likert-like data using the ggplot2 plotting engine
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licorice is an R package that eases the plotting of Likert-like data. It has been heavily inspired by the likert package from Bryer and Speerschneider.

licorice makes use of the ggplot2 plotting engine in such a way that interference by the licorice package in terms of theming is kept to a minimum (the graphs diplayed belowed are themed using the ggthemr package). When using the licorice function a ggplot2 object is returned which can then be added upon to your liking.

Installation

For now, no CRAN version exists and you'll have to install from GitHub using devtools.

devtools::install_github("Bart6114/licorice")

Preparing the data

The licorice function expects a given structure of data. The example pisatest dataset can be used as a reference.

A minimal requirement is the presence of the question, response and count column. Additionally a group column can be added.

library(licorice)

## Warning: replacing previous import by 'tidyr::%>%' when loading 'licorice'

head(pisatest)

##   question response         group count
## 1  ST24Q01    Agree        Canada  5623
## 2  ST24Q01    Agree        Mexico 12622
## 3  ST24Q01    Agree United States  1755
## 4  ST24Q01 Disagree        Canada  7938
## 5  ST24Q01 Disagree        Mexico 13872
## 6  ST24Q01 Disagree United States  1705

For example the gapsample dataset is not structured as it should be. Some simple preparations make it suited for licorice.

head(gapsample)

##   StudentId      question          response
## 1         1 Financial Aid             Agree
## 2         2 Financial Aid Strongly disagree
## 3         3 Financial Aid    Agree somewhat
## 4         4 Financial Aid    Strongly agree
## 5         5 Financial Aid    Strongly agree
## 6         6 Financial Aid             Agree

library(dplyr)
gap_fixed<-
  gapsample %>%
  group_by(question, response) %>%
  summarise(count = n())

head(gap_fixed)

## Source: local data frame [6 x 3]
## Groups: question [1]
## 
##        question          response count
##          (fctr)            (fctr) (int)
## 1 Financial Aid Strongly disagree     7
## 2 Financial Aid          Disagree     3
## 3 Financial Aid Disagree somewhat     2
## 4 Financial Aid         Undecided     3
## 5 Financial Aid    Agree somewhat     9
## 6 Financial Aid             Agree     7

Plotting the data

Three main plots are available. First a centered plot is shown; here the junction between two categories (which can be controlled by the middle_pos parameter) is centered. If the factor levels of the reponse variable are not set correctly, they can be specified using the answer_order parameter. If a middle_pos value of e.g. 2 is given, the results are centered at the junction between the second and third response type.

my_order<-
  c("Strongly disagree","Disagree", "Agree", "Strongly agree")


licorice(pisatest, answers_order = my_order, middle_pos = 2, type = "center", sort=T)

One can also fill the vertical space using a filled plot (also notice the sort argument).

licorice(pisatest, answers_order = my_order, type = "fill", sort=TRUE)

We can also have a look at the count data.

licorice(pisatest, answers_order = my_order, type = "count")

You can also show plots in combination with each other using existing functionality (the gridExtra library).

library(gridExtra)

grid.arrange(
  licorice(pisatest, my_order, middle_pos = 2.5, type = "center", sort=TRUE),
  licorice(pisatest, my_order, type = "count", sort=TRUE) +
    theme(axis.text.y=element_blank()) +
    scale_fill_discrete(""),
  ncol = 2,
  widths = c(3/4,1/4)
)

Groups (as the countries in the graph above) are shown automatically when a group column is available in the data set. For example, when using the generated gap_fixed data set (where not group column is present), no group is shown;

levels(gap_fixed$response)

## [1] "Strongly disagree" "Disagree"          "Disagree somewhat"
## [4] "Undecided"         "Agree somewhat"    "Agree"            
## [7] "Strongly agree"

licorice(gap_fixed, middle_pos = 4, sort=TRUE) +
  theme(legend.position="right")