/ggstatsplot

Collection of functions to enhance ggplot2 plots with results from statistical tests.

Primary LanguageRGNU General Public License v3.0GPL-3.0

ggstatsplot: ggplot2 Based Plots with Statistical Details

packageversion Travis Build Status AppVeyor Build Status Licence Project Status: Active - The project has reached a stable, usable state and is being actively developed. Last-changedate lifecycle minimal R version

Overview

ggstatsplot is an extension of ggplot2 package for creating graphics with details from statistical tests included in the plots themselves and targeted primarily at behavioral sciences community to provide a one-line code to produce information-rich figures. Currently, it supports only the most common types of tests used in analysis (parametric, nonparametric, and robust versions of t-tets/anova, correlation, and contingency tables analyses). Future versions will include other types of analyses as well.

Installation

You can get the development version from GitHub. If you are in hurry and want to reduce the time of installation, prefer-

# install.packages("devtools")                                # needed package to download from GitHub repo
devtools::install_github(repo = "IndrajeetPatil/ggstatsplot", # package path on GitHub
                         quick = TRUE)                        # skips docs, demos, and vignettes

If time is not a constraint-

devtools::install_github(repo = "IndrajeetPatil/ggstatsplot", # package path on GitHub
                         dependencies = TRUE,                 # installs packages which ggstatsplot depends on
                         upgrade_dependencies = TRUE          # updates any out of date dependencies
)

Help

Documentation for any function can be accessed with the standard help command-

?ggbetweenstats
?ggscatterstats
?gghistostats
?ggpiestats
?ggcorrmat
?combine_plots

Usage

Here are examples of the main functions currently supported in ggstatsplot:

  • ggbetweenstats

This function creates a violin plot for between-group or between-condition comparisons with results from statistical tests in the subtitle:

ggstatsplot::ggbetweenstats(data = iris, 
                            x = Species, 
                            y = Sepal.Length)
#> Reference:  Welch's ANOVA is used as a default. (Delacre, Leys, Mora, & Lakens, PsyArXiv, 2018).Note:  Shapiro-Wilk test of normality for Sepal.Length : p-value =  0.010Note:  Bartlett's test for homogeneity of variances for factor Species : p-value =  < 0.001

Number of other arguments can be specified to make this plot even more informative and, additionally, this function returns a ggplot2 object and thus any of the graphics layers can be further modified:

library(ggplot2)

ggstatsplot::ggbetweenstats(
  data = iris,
  x = Species,
  y = Sepal.Length,
  mean.plotting = TRUE,                           # whether mean for each group id to be displayed 
  type = "robust",                                # which type of test is to be run
  outlier.tagging = TRUE,                         # whether outliers need to be tagged
  outlier.label = Sepal.Width,                    # variable to be used for the outlier tag
  xlab = "Type of Species",                       # label for the x-axis variable
  ylab = "Attribute: Sepal Length",               # label for the y-axis variable
  title = "Dataset: Iris flower data set",        # title text for the plot
  caption = expression(                           # caption text for the plot 
    paste(italic("Note"), ": this is a demo")
    )
  ) +                                             # further modifcation outside of ggstatsplot
  ggplot2::coord_cartesian(ylim = c(3, 8)) + 
  ggplot2::scale_y_continuous(breaks = seq(3, 8, by = 1)) 
#> Note:  Shapiro-Wilk test of normality for Sepal.Length : p-value =  0.010Note:  Bartlett's test for homogeneity of variances for factor Species : p-value =  < 0.001

Variant of this function ggwithinstats is currently under work.

  • ggscatterstats

This function creates a scatterplot with marginal histograms/boxplots/density/violin plots from ggExtra::ggMarginal() and results from statistical tests in the subtitle:

ggstatsplot::ggscatterstats(data = iris, 
                            x = Sepal.Length, 
                            y = Petal.Length,
                            title = "Dataset: Iris flower data set")
#> Warning: This function doesn't return ggplot2 object and is not further modifiable with ggplot2 commands.

Number of other arguments can be specified to modify this basic plot-

library(datasets)

ggstatsplot::ggscatterstats(
  data = subset(iris, iris$Species == "setosa"),
  x = Sepal.Length,
  y = Petal.Length,
  test = "robust",                               # type of test that needs to be run
  xlab = "Attribute: Sepal Length",              # label for x axis
  ylab = "Attribute: Petal Length",              # label for y axis 
  line.colour = "black",                         # changing regression line colour line
  title = "Dataset: Iris flower data set",       # title text for the plot
  caption = expression(                          # caption text for the plot
    paste(italic("Note"), ": this is a demo")
    ),
  marginal.type = "density",                     # type of marginal distribution to be displayed
  xfill = "blue",                                # colour fill for x-axis marginal distribution 
  yfill = "red",                                 # colour fill for y-axis marginal distribution
  intercept = "median",                          # which type of intercept line is to be displayed  
  width.jitter = 0.2,                            # amount of horizontal jitter for data points
  height.jitter = 0.4                            # amount of vertical jitter for data points
  ) 
#> Note: Standardized robust regression using an M estimator: no. of iterations = 1000 In case of non-convergence, increase maxit value.Warning: This function doesn't return ggplot2 object and is not further modifiable with ggplot2 commands.

Important: In contrast to all other functions in this package, the ggscatterstats function returns object that is not further modifiable with ggplot2. This can be avoided by not plotting the marginal distributions (marginal = FALSE). Currently trying to find a workaround this problem.

  • ggpiestats

This function creates a pie chart for categorical variables with results from contingency table analysis included in the subtitle of the plot. If only one categorical variable is entered, proportion test will be carried out.

ggstatsplot::ggpiestats(data = iris,
                        main = Species)
#> Warning: No guarantee this function will work properly if you are using development version of ggplot2 (2.2.1.9000)

This function can also be used to study an interaction between two categorical variables. Additionally, as with the other functions in ggstatsplot, this function returns a ggplot2 object and can further be modified with ggplot2 syntax (e.g., we can change the color palette after ggstatsplot has produced the plot)-

library(ggplot2)

ggstatsplot::ggpiestats(data = mtcars,
                        main = am,                
                        condition = cyl) +
  ggplot2::scale_fill_brewer(palette = "Dark2")   # further modifcation outside of ggstatsplot    
#> Warning: No guarantee this function will work properly if you are using development version of ggplot2 (2.2.1.9000)

As with the other functions, this basic plot can further be modified with additional arguments:

library(ggplot2)

ggstatsplot::ggpiestats(
  data = mtcars,
  main = am,
  condition = cyl,
  title = "Dataset: Motor Trend Car Road Tests",      # title for the plot
  stat.title = "interaction effect",                  # title for the results from Pearson's chi-squared test
  legend.title = "Transmission",                      # title for the legend
  factor.levels = c("0 = automatic", "1 = manual"),   # renaming the factor level names for main variable 
  facet.wrap.name = "No. of cylinders",               # name for the facetting variable
  caption = expression(                               # text for the caption
    paste(italic("Note"), ": this is a demo")
    )
) 
#> Warning: No guarantee this function will work properly if you are using development version of ggplot2 (2.2.1.9000)

  • gghistostats

In case you would like to see the distribution of one variable and check if it is significantly different from a specified value with a one sample test, this function will let you do that.

library(datasets)
library(viridis)

ggstatsplot::gghistostats(
  data = iris,
  x = Sepal.Length,
  title = "Distribution of Iris sepal length",
  type = "parametric",            # one sample t-test
  test.value = 3,                 # default value is 0
  centrality.para = "mean",       # which measure of central tendency is to be plotted
  centrality.colour = "red",      # decides colour of vertical line representing central tendency
  density.plot = TRUE,            # whether density plot is to be overlayed on a histogram
  binwidth.adjust = TRUE,         # whether binwidth needs to be adjusted
  binwidth = 0.10                 # binwidth value (needs to be toyed around with until you find the best one)
) +              
  viridis::scale_fill_viridis()   # further modifcation outside of ggstatsplot
#> Note:  Shapiro-Wilk test of normality for Sepal.Length : p-value =  0.010

  • ggcorrmat

ggcorrmat makes correlalograms with minimal amount of code. Just sticking to the defaults itself produces publication-ready correlation matrices. (Wrapper around ggcorrplot)

# as a default this function outputs a correlalogram plot
ggstatsplot::ggcorrmat(
  data = iris,
  corr.method = "spearman",      # correlation method
  sig.level = 0.005,              # threshold of significance
  cor.vars = c(Sepal.Length, Sepal.Width, Petal.Length, Petal.Width),
  cor.vars.names = c("Sepal Length", "Sepal Width", "Petal Length", "Petal Width"),
  title = "Correlalogram for length measures for Iris species",
  subtitle = "Iris dataset by Anderson",
  caption = expression(
    paste(
      italic("Note"),
      ": X denotes correlation non-significant at ",
      italic("p "),
      "< 0.005; adjusted alpha"
    )
  )
)

Alternatively, you can use it just to get the correlation matrices and their corresponding p-values (in a tibble format).

# getting correlations 
ggstatsplot::ggcorrmat(
  data = iris,
  cor.vars = c(Sepal.Length, Sepal.Width, Petal.Length, Petal.Width),
  output = "correlations"
)
#> # A tibble: 4 x 5
#>   variable     Sepal.Length Sepal.Width Petal.Length Petal.Width
#>   <chr>               <dbl>       <dbl>        <dbl>       <dbl>
#> 1 Sepal.Length        1.00       -0.120        0.870       0.820
#> 2 Sepal.Width        -0.120       1.00        -0.430      -0.370
#> 3 Petal.Length        0.870      -0.430        1.00        0.960
#> 4 Petal.Width         0.820      -0.370        0.960       1.00

# getting p-values
ggstatsplot::ggcorrmat(
  data = iris,
  cor.vars = c(Sepal.Length, Sepal.Width, Petal.Length, Petal.Width),
  output = "p-values"
)
#> # A tibble: 4 x 5
#>   variable     Sepal.Length  Sepal.Width Petal.Length Petal.Width
#>   <chr>               <dbl>        <dbl>        <dbl>       <dbl>
#> 1 Sepal.Length     0.       0.152            1.04e-47    2.33e-37
#> 2 Sepal.Width      1.52e- 1 0.               4.51e- 8    4.07e- 6
#> 3 Petal.Length     1.04e-47 0.0000000451     0.          4.68e-86
#> 4 Petal.Width      2.33e-37 0.00000407       4.68e-86    0.
  • combine_plots

ggstatsplot also contains a helper function combine_plots to combine multiple plots. This is a wrapper around cowplot::plot_grid and lets you combine multiple plots and add combination of title, caption, and annotation texts with suitable default parameters.

The full power of ggstatsplot can be leveraged with a functional programming package like purrr that replaces many for loops with code that is both more succinct and easier to read and, therefore, purrr should be preferrred.

An example is provided below. Notice how little code is needed not only to prepare the plots but also to plot the statistical test results.

library(glue)
library(tidyverse)

### creating a list column with `ggstatsplot` plots
plots <- datasets::iris %>%
  dplyr::mutate(.data = ., Species2 = Species) %>% # just creates a copy of this variable
  dplyr::group_by(.data = ., Species) %>%                
  tidyr::nest(data = .) %>%                        # creates a nested dataframe with list column called `data`
  dplyr::mutate(                                   # creating a new list column of ggstatsplot outputs
    .data = .,
    plot = data %>%
      purrr::map(
        .x = .,
        .f = ~ ggstatsplot::ggscatterstats(
          data = .,
          x = Sepal.Length,
          y = Sepal.Width,
          marginal.type = "boxplot",
          title =
            glue::glue("Species: {.$Species2} (n = {length(.$Sepal.Length)})")
        )
      )
  )
#> Warning: This function doesn't return ggplot2 object and is not further modifiable with ggplot2 commands.Warning: This function doesn't return ggplot2 object and is not further modifiable with ggplot2 commands.Warning: This function doesn't return ggplot2 object and is not further modifiable with ggplot2 commands.

### display the new object (notice that the class of the `plot` list column is S3: gg)
plots
#> # A tibble: 3 x 3
#>   Species    data              plot             
#>   <fct>      <list>            <list>           
#> 1 setosa     <tibble [50 x 5]> <S3: ggExtraPlot>
#> 2 versicolor <tibble [50 x 5]> <S3: ggExtraPlot>
#> 3 virginica  <tibble [50 x 5]> <S3: ggExtraPlot>

### creating a grid with cowplot
ggstatsplot::combine_plots(
  plotlist = plots$plot,                           # list column containing all ggstatsplot objects
  labels = c("(a)", "(b)", "(c)"),
  nrow = 3,
  ncol = 1,
  title.text = "Relationship between sepal length and width for all Iris species",
  title.size = 14,
  title.colour = "blue",
  caption.text = expression(
    paste(
      italic("Note"),
      ": Iris flower dataset was collected by Edgar Anderson."
    ),
    caption.size = 10
  )
)

Here is another example with ggbetweenstats-

library(tidyverse)
library(glue)

### creating a list column with `ggstatsplot` plots
plots <- datasets::mtcars %>%
  dplyr::mutate(.data = ., cyl2 = cyl) %>%        # just creates a copy of this variable
  dplyr::group_by(.data = ., cyl) %>%             # 
  tidyr::nest(data = .) %>%                       # creates a nested dataframe with list column called `data`
  dplyr::mutate(                                  # creating a new list column of ggstatsplot outputs
    .data = .,
    plot = data %>%
      purrr::map(
        .x = .,
        .f = ~ ggstatsplot::ggbetweenstats(
          data = .,
          x = am,
          y = mpg,
          xlab = "Transmission",
          ylab = "Miles/(US) gallon",
          title = glue::glue(
            "Number of cylinders: {.$cyl2}"        # this is where the duplicated cyl2 column is useful
            ) 
        )
      )
  )
#> Warning:  aesthetic `x` was not a factor; converting it to factorReference:  Welch's t-test is used as a default. (Delacre, Lakens, & Leys, International Review of Social Psychology, 2017).Note:  Shapiro-Wilk test of normality for mpg : p-value =  0.325Note:  Bartlett's test for homogeneity of variances for factor am : p-value =  0.317Warning:  aesthetic `x` was not a factor; converting it to factorReference:  Welch's t-test is used as a default. (Delacre, Lakens, & Leys, International Review of Social Psychology, 2017).Note:  Shapiro-Wilk test of normality for mpg : p-value =  0.261Note:  Bartlett's test for homogeneity of variances for factor am : p-value =  0.144Warning:  aesthetic `x` was not a factor; converting it to factorReference:  Welch's t-test is used as a default. (Delacre, Lakens, & Leys, International Review of Social Psychology, 2017).Note:  Shapiro-Wilk test of normality for mpg : p-value =  0.323Note:  Bartlett's test for homogeneity of variances for factor am : p-value =  0.201

### display the new object (notice that the class of the `plot` list column is S3: gg)
plots
#> # A tibble: 3 x 3
#>     cyl data               plot    
#>   <dbl> <list>             <list>  
#> 1    6. <tibble [7 x 11]>  <S3: gg>
#> 2    4. <tibble [11 x 11]> <S3: gg>
#> 3    8. <tibble [14 x 11]> <S3: gg>

### creating a grid with cowplot
ggstatsplot::combine_plots(plotlist = plots$plot,       # list column containing all ggstatsplot objects
                           nrow = 3,
                           ncol = 1,
                           labels = c("(a)","(b)","(c)"),
                           title.text = "MPG and car transmission relationship (for each cylinder count)",
                           title.size = 13,
                           title.colour = "blue",
                           caption.text = expression(
                             paste(
                               italic("Transmission"),
                               ": 0 = automatic, 1 = manual"
                             ),
                             caption.size = 10
                           ))

  • theme_mprl

ggstatsplot uses a default theme theme_mprl() that can be used with any ggplot2 objects.

library(ggplot2)

# Basic scatter plot
ggplot(mtcars, aes(x = wt, y = mpg)) + 
  geom_point()

# Basic scatter plot with theme_mprl() added
ggplot(mtcars, aes(x = wt, y = mpg)) + 
  geom_point() + 
  ggstatsplot::theme_mprl()

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