{statsExpressions}
: Tidy dataframes and expressions with statistical detailsStatus | Usage | Miscellaneous |
---|---|---|
The {statsExpressions}
package has two key aims:
Statistical packages exhibit substantial diversity in terms of their syntax and expected input type. This can make it difficult to switch from one statistical approach to another. For example, some functions expect vectors as inputs, while others expect dataframes. Depending on whether it is a repeated measures design or not, different functions might expect data to be in wide or long format. Some functions can internally omit missing values, while other functions error in their presence. Furthermore, if someone wishes to utilize the objects returned by these packages downstream in their workflow, this is not straightforward either because even functions from the same package can return a list, a matrix, an array, a dataframe, etc., depending on the function.
This is where {statsExpressions}
comes in: It can be thought of as a unified portal through which most of the functionality in these underlying packages can be accessed, with a simpler interface and no requirement to change data format.
This package forms the statistical processing backend for ggstatsplot
package.
For more documentation, see the dedicated website.
Type | Source | Command |
---|---|---|
Release | install.packages("statsExpressions") |
|
Development | remotes::install_github("IndrajeetPatil/statsExpressions") |
The package can be cited as:
citation("statsExpressions")
Patil, I., (2021). statsExpressions: R Package for Tidy Dataframes
and Expressions with Statistical Details. Journal of Open Source
Software, 6(61), 3236, https://doi.org/10.21105/joss.03236
A BibTeX entry for LaTeX users is
@Article{,
doi = {10.21105/joss.03236},
url = {https://doi.org/10.21105/joss.03236},
year = {2021},
publisher = {{The Open Journal}},
volume = {6},
number = {61},
pages = {3236},
author = {Indrajeet Patil},
title = {{statsExpressions: {R} Package for Tidy Dataframes and Expressions with Statistical Details}},
journal = {{Journal of Open Source Software}},
}
Summary of available analyses
Summary of details available for analyses
Analysis | Hypothesis testing | Effect size estimation |
---|---|---|
(one/two-sample) t-test | ✅ | ✅ |
one-way ANOVA | ✅ | ✅ |
correlation | ✅ | ✅ |
(one/two-way) contingency table | ✅ | ✅ |
random-effects meta-analysis | ✅ | ✅ |
Summary of supported statistical approaches
Description | Parametric | Non-parametric | Robust | Bayesian |
---|---|---|---|---|
Between group/condition comparisons | ✅ | ✅ | ✅ | ✅ |
Within group/condition comparisons | ✅ | ✅ | ✅ | ✅ |
Distribution of a numeric variable | ✅ | ✅ | ✅ | ✅ |
Correlation between two variables | ✅ | ✅ | ✅ | ✅ |
Association between categorical variables | ✅ | ✅ | ❌ | ✅ |
Equal proportions for categorical variable levels | ✅ | ✅ | ❌ | ✅ |
Random-effects meta-analysis | ✅ | ❌ | ✅ | ✅ |
To illustrate the simplicity of this syntax, let’s say we want to run a one-way ANOVA. If we first run a non-parametric ANOVA and then decide to run a robust ANOVA instead, the syntax remains the same and the statistical approach can be modified by changing a single argument:
library(statsExpressions)
mtcars %>% oneway_anova(cyl, wt, type = "nonparametric")
#> # A tibble: 1 x 15
#> parameter1 parameter2 statistic df.error p.value
#> <chr> <chr> <dbl> <int> <dbl>
#> 1 wt cyl 22.8 2 0.0000112
#> method effectsize estimate conf.level conf.low
#> <chr> <chr> <dbl> <dbl> <dbl>
#> 1 Kruskal-Wallis rank sum test Epsilon2 (rank) 0.736 0.95 0.624
#> conf.high conf.method conf.iterations n.obs expression
#> <dbl> <chr> <int> <int> <list>
#> 1 1 percentile bootstrap 100 32 <expression>
mtcars %>% oneway_anova(cyl, wt, type = "robust")
#> # A tibble: 1 x 12
#> statistic df df.error p.value
#> <dbl> <dbl> <dbl> <dbl>
#> 1 12.7 2 12.2 0.00102
#> method
#> <chr>
#> 1 A heteroscedastic one-way ANOVA for trimmed means
#> effectsize estimate conf.level conf.low conf.high
#> <chr> <dbl> <dbl> <dbl> <dbl>
#> 1 Explanatory measure of effect size 1.05 0.95 0.843 1.50
#> n.obs expression
#> <int> <list>
#> 1 32 <expression>
All possible output dataframes from functions are tabulated here: https://indrajeetpatil.github.io/statsExpressions/articles/web_only/dataframe_outputs.html
Needless to say this will also work with the kable
function to generate a table:
# setup
library(statsExpressions)
set.seed(123)
# one-sample robust t-test
# we will leave `expression` column out; it's not needed for using only the dataframe
mtcars %>%
one_sample_test(wt, test.value = 3, type = "robust") %>%
dplyr::select(-expression) %>%
knitr::kable()
statistic | p.value | n.obs | method | effectsize | estimate | conf.level | conf.low | conf.high |
---|---|---|---|---|---|---|---|---|
1.179181 | 0.275 | 32 | Bootstrap-t method for one-sample test | Trimmed mean | 3.197 | 0.95 | 2.854246 | 3.539754 |
These functions are also compatible with other popular data manipulation packages.
For example, let’s say we want to run a one-sample t-test for all levels of a certain grouping variable. We can use dplyr
to do so:
# for reproducibility
set.seed(123)
library(dplyr)
# grouped operation
# running one-sample test for all levels of grouping variable `cyl`
mtcars %>%
group_by(cyl) %>%
group_modify(~ one_sample_test(.x, wt, test.value = 3), .keep = TRUE) %>%
ungroup()
#> # A tibble: 3 x 16
#> cyl mu statistic df.error p.value method alternative
#> <dbl> <dbl> <dbl> <dbl> <dbl> <chr> <chr>
#> 1 4 3 -4.16 10 0.00195 One Sample t-test two.sided
#> 2 6 3 0.870 6 0.418 One Sample t-test two.sided
#> 3 8 3 4.92 13 0.000278 One Sample t-test two.sided
#> effectsize estimate conf.level conf.low conf.high conf.method
#> <chr> <dbl> <dbl> <dbl> <dbl> <chr>
#> 1 Hedges' g -1.16 0.95 -1.97 -0.422 ncp
#> 2 Hedges' g 0.286 0.95 -0.419 1.01 ncp
#> 3 Hedges' g 1.24 0.95 0.565 1.98 ncp
#> conf.distribution n.obs expression
#> <chr> <int> <list>
#> 1 t 11 <expression>
#> 2 t 7 <expression>
#> 3 t 14 <expression>
Note that expression here means a pre-formatted in-text statistical result. In addition to other details contained in the dataframe, there is also a column titled expression
, which contains expression with statistical details and can be displayed in a plot.
For all statistical test expressions, the default template attempt to follow the gold standard for statistical reporting.
For example, here are results from Welch’s t-test:
library(ggplot2)
# displaying mean for each level of `cyl`
centrality_description(mtcars, cyl, wt) |>
ggplot(aes(cyl, wt)) +
geom_point() +
geom_label(aes(label = expression), parse = TRUE)
Here are a few examples for supported analyses.
Let’s say we want to check differences in weight of the vehicle based on number of cylinders in the engine and wish to carry out robust trimmed-means ANOVA:
# setup
set.seed(123)
library(ggplot2)
library(statsExpressions)
library(ggridges)
# create a ridgeplot
ggplot(iris, aes(x = Sepal.Length, y = Species)) +
geom_density_ridges(
jittered_points = TRUE, quantile_lines = TRUE,
scale = 0.9, vline_size = 1, vline_color = "red",
position = position_raincloud(adjust_vlines = TRUE)
) + # use the expression in the dataframe to display results in the subtitle
labs(
title = "A heteroscedastic one-way ANOVA for trimmed means",
subtitle = oneway_anova(iris, Species, Sepal.Length, type = "robust")$expression[[1]]
)
Let’s now see an example of a repeated measures one-way ANOVA.
# setup
set.seed(123)
library(ggplot2)
library(WRS2)
library(ggbeeswarm)
library(statsExpressions)
ggplot2::ggplot(WineTasting, aes(Wine, Taste, color = Wine)) +
geom_quasirandom() +
labs(
title = "Friedman's rank sum test",
subtitle = oneway_anova(
WineTasting,
Wine,
Taste,
paired = TRUE,
subject.id = Taster,
type = "np"
)$expression[[1]]
)
# setup
set.seed(123)
library(ggplot2)
library(gghalves)
library(ggbeeswarm)
library(hrbrthemes)
# create a plot
ggplot(ToothGrowth, aes(supp, len)) +
geom_half_boxplot() +
geom_beeswarm() +
theme_ipsum_rc() +
# adding a subtitle with
labs(
title = "Two-Sample Welch's t-test",
subtitle = two_sample_test(ToothGrowth, supp, len)$expression[[1]]
)
We can also have a look at a repeated measures design and the related expressions.
# setup
set.seed(123)
library(ggplot2)
library(tidyr)
library(PairedData)
data(PrisonStress)
# get data in tidy format
df <- pivot_longer(PrisonStress, starts_with("PSS"), "PSS", values_to = "stress")
# plot
paired.plotProfiles(PrisonStress, "PSSbefore", "PSSafter", subjects = "Subject") +
labs(
title = "Two-sample Wilcoxon paired test",
subtitle = two_sample_test(
data = df,
x = PSS,
y = stress,
paired = TRUE,
subject.id = Subject,
type = "np"
)$expression[[1]]
)
# setup
set.seed(123)
library(ggplot2)
# dataframe with results
df_results <- one_sample_test(mtcars, wt,
test.value = 3, type = "bayes",
top.text = "Bayesian one-sample t-test"
)
# creating a histogram plot
ggplot(mtcars, aes(wt)) +
geom_histogram(alpha = 0.5) +
geom_vline(xintercept = mean(mtcars$wt), color = "red") +
labs(
subtitle = df_results$expression[[1]]
)
Let’s look at another example where we want to run correlation analysis:
# setup
set.seed(123)
library(ggplot2)
# create a scatter plot
ggplot(mtcars, aes(mpg, wt)) +
geom_point() +
geom_smooth(method = "lm", formula = y ~ x) +
labs(
title = "Spearman's rank correlation coefficient",
subtitle = corr_test(mtcars, mpg, wt, type = "nonparametric")$expression[[1]]
)
For categorical/nominal data - one-sample:
# setup
set.seed(123)
library(ggplot2)
df_results <- contingency_table(as.data.frame(table(mpg$class)),
Var1,
counts = Freq,
type = "bayes",
top.text = "One-sample goodness-of-fit test"
)
# basic pie chart
ggplot(as.data.frame(table(mpg$class)), aes(x = "", y = Freq, fill = factor(Var1))) +
geom_bar(width = 1, stat = "identity") +
theme(axis.line = element_blank()) +
# cleaning up the chart and adding results from one-sample proportion test
coord_polar(theta = "y", start = 0) +
labs(
fill = "Class",
x = NULL,
y = NULL,
title = "Pie Chart of class (type of car)",
caption = df_results$expression[[1]]
)
You can also use these function to get the expression in return without having to display them in plots:
# setup
set.seed(123)
library(ggplot2)
# Pearson's chi-squared test of independence
contingency_table(mtcars, am, cyl)$expression[[1]]
#> expression(list(chi["Pearson"]^2 * "(" * 2 * ")" == "8.74", italic(p) ==
#> "0.01", widehat(italic("V"))["Cramer"] == "0.46", CI["95%"] ~
#> "[" * "0.00", "1.00" * "]", italic("n")["obs"] == "32"))
# setup
set.seed(123)
library(metaviz)
library(ggplot2)
library(metaplus)
# meta-analysis forest plot with results random-effects meta-analysis
viz_forest(
x = mozart[, c("d", "se")],
study_labels = mozart[, "study_name"],
xlab = "Cohen's d",
variant = "thick",
type = "cumulative"
) + # use `{statsExpressions}` to create expression containing results
labs(
title = "Meta-analysis of Pietschnig, Voracek, and Formann (2010) on the Mozart effect",
subtitle = meta_analysis(dplyr::rename(mozart, estimate = d, std.error = se))$expression[[1]]
) +
theme(text = element_text(size = 12))
Sometimes you may not wish include so many details in the subtitle. In that case, you can extract the expression and copy-paste only the part you wish to include. For example, here only statistic and p-values are included:
# setup
set.seed(123)
library(ggplot2)
# extracting detailed expression
(res_expr <- oneway_anova(iris, Species, Sepal.Length, var.equal = TRUE)$expression[[1]])
#> expression(list(italic("F")["Fisher"](2, 147) == "119.26", italic(p) ==
#> "1.67e-31", widehat(omega["p"]^2) == "0.61", CI["95%"] ~
#> "[" * "0.53", "1.00" * "]", italic("n")["obs"] == "150"))
# adapting the details to your liking
ggplot(iris, aes(x = Species, y = Sepal.Length)) +
geom_boxplot() +
labs(subtitle = ggplot2::expr(paste(
NULL, italic("F"), "(", "2",
",", "147", ") = ", "119.26", ", ",
italic("p"), " = ", "1.67e-31"
)))
Here a go-to summary about statistical test carried out and the returned effect size for each function is provided. This should be useful if one needs to find out more information about how an argument is resolved in the underlying package or if one wishes to browse the source code. So, for example, if you want to know more about how one-way (between-subjects) ANOVA, you can run ?stats::oneway.test
in your R console.
centrality_description
Type | Measure | Function used |
---|---|---|
Parametric | mean | parameters::describe_distribution() |
Non-parametric | median | parameters::describe_distribution() |
Robust | trimmed mean | parameters::describe_distribution() |
Bayesian | MAP (maximum a posteriori probability) estimate | parameters::describe_distribution() |
oneway_anova
Hypothesis testing
Type | No. of groups | Test | Function used |
---|---|---|---|
Parametric | > 2 | Fisher’s or Welch’s one-way ANOVA | stats::oneway.test() |
Non-parametric | > 2 | Kruskal-Wallis one-way ANOVA | stats::kruskal.test() |
Robust | > 2 | Heteroscedastic one-way ANOVA for trimmed means | WRS2::t1way() |
Bayes Factor | > 2 | Fisher’s ANOVA | BayesFactor::anovaBF() |
Effect size estimation
Type | No. of groups | Effect size | CI available? | Function used |
---|---|---|---|---|
Parametric | > 2 | partial eta-squared, partial omega-squared | Yes | effectsize::omega_squared() , effectsize::eta_squared() |
Non-parametric | > 2 | rank epsilon squared | Yes | effectsize::rank_epsilon_squared() |
Robust | > 2 | Explanatory measure of effect size | Yes | WRS2::t1way() |
Bayes Factor | > 2 | Bayesian R-squared | Yes | performance::r2_bayes() |
Hypothesis testing
Type | No. of groups | Test | Function used |
---|---|---|---|
Parametric | > 2 | One-way repeated measures ANOVA | afex::aov_ez() |
Non-parametric | > 2 | Friedman rank sum test | stats::friedman.test() |
Robust | > 2 | Heteroscedastic one-way repeated measures ANOVA for trimmed means | WRS2::rmanova() |
Bayes Factor | > 2 | One-way repeated measures ANOVA | BayesFactor::anovaBF() |
Effect size estimation
Type | No. of groups | Effect size | CI available? | Function used |
---|---|---|---|---|
Parametric | > 2 | partial eta-squared, partial omega-squared | Yes | effectsize::omega_squared() , effectsize::eta_squared() |
Non-parametric | > 2 | Kendall’s coefficient of concordance | Yes | effectsize::kendalls_w() |
Robust | > 2 | Algina-Keselman-Penfield robust standardized difference average | Yes | WRS2::wmcpAKP() |
Bayes Factor | > 2 | Bayesian R-squared | Yes | performance::r2_bayes() |
two_sample_test
Hypothesis testing
Type | No. of groups | Test | Function used |
---|---|---|---|
Parametric | 2 | Student’s or Welch’s t-test | stats::t.test() |
Non-parametric | 2 | Mann-Whitney U test | stats::wilcox.test() |
Robust | 2 | Yuen’s test for trimmed means | WRS2::yuen() |
Bayesian | 2 | Student’s t-test | BayesFactor::ttestBF() |
Effect size estimation
Type | No. of groups | Effect size | CI available? | Function used |
---|---|---|---|---|
Parametric | 2 | Cohen’s d, Hedge’s g | Yes | effectsize::cohens_d() , effectsize::hedges_g() |
Non-parametric | 2 | r (rank-biserial correlation) | Yes | effectsize::rank_biserial() |
Robust | 2 | Algina-Keselman-Penfield robust standardized difference | Yes | WRS2::akp.effect() |
Bayesian | 2 | difference | Yes | bayestestR::describe_posterior() |
Hypothesis testing
Type | No. of groups | Test | Function used |
---|---|---|---|
Parametric | 2 | Student’s t-test | stats::t.test() |
Non-parametric | 2 | Wilcoxon signed-rank test | stats::wilcox.test() |
Robust | 2 | Yuen’s test on trimmed means for dependent samples | WRS2::yuend() |
Bayesian | 2 | Student’s t-test | BayesFactor::ttestBF() |
Effect size estimation
Type | No. of groups | Effect size | CI available? | Function used |
---|---|---|---|---|
Parametric | 2 | Cohen’s d, Hedge’s g | Yes | effectsize::cohens_d() , effectsize::hedges_g() |
Non-parametric | 2 | r (rank-biserial correlation) | Yes | effectsize::rank_biserial() |
Robust | 2 | Algina-Keselman-Penfield robust standardized difference | Yes | WRS2::wmcpAKP() |
Bayesian | 2 | difference | Yes | bayestestR::describe_posterior() |
one_sample_test
Hypothesis testing
Type | Test | Function used |
---|---|---|
Parametric | One-sample Student’s t-test | stats::t.test |
Non-parametric | One-sample Wilcoxon test | stats::wilcox.test |
Robust | Bootstrap-t method for one-sample test | WRS2::trimcibt |
Bayesian | One-sample Student’s t-test | BayesFactor::ttestBF |
Effect size estimation
Type | Effect size | CI available? | Function used |
---|---|---|---|
Parametric | Cohen’s d, Hedge’s g | Yes | effectsize::cohens_d() , effectsize::hedges_g() |
Non-parametric | r (rank-biserial correlation) | Yes | effectsize::rank_biserial() |
Robust | trimmed mean | Yes | WRS2::trimcibt() |
Bayes Factor | difference | Yes | bayestestR::describe_posterior() |
corr_test
Hypothesis testing and Effect size estimation
Type | Test | CI available? | Function used |
---|---|---|---|
Parametric | Pearson’s correlation coefficient | Yes | correlation::correlation() |
Non-parametric | Spearman’s rank correlation coefficient | Yes | correlation::correlation() |
Robust | Winsorized Pearson correlation coefficient | Yes | correlation::correlation() |
Bayesian | Bayesian Pearson’s correlation coefficient | Yes | correlation::correlation() |
contingency_table
Hypothesis testing
Type | Design | Test | Function used |
---|---|---|---|
Parametric/Non-parametric | Unpaired | Pearson’s chi-squared test | stats::chisq.test() |
Bayesian | Unpaired | Bayesian Pearson’s chi-squared test | BayesFactor::contingencyTableBF() |
Parametric/Non-parametric | Paired | McNemar’s chi-squared test | stats::mcnemar.test() |
Bayesian | Paired | No | No |
Effect size estimation
Type | Design | Effect size | CI available? | Function used |
---|---|---|---|---|
Parametric/Non-parametric | Unpaired | Cramer’s V | Yes | effectsize::cramers_v() |
Bayesian | Unpaired | Cramer’s V | Yes | effectsize::cramers_v() |
Parametric/Non-parametric | Paired | Cohen’s g | Yes | effectsize::cohens_g() |
Bayesian | Paired | No | No | No |
Hypothesis testing
Type | Test | Function used |
---|---|---|
Parametric/Non-parametric | Goodness of fit chi-squared test | stats::chisq.test() |
Bayesian | Bayesian Goodness of fit chi-squared test | (custom) |
Effect size estimation
Type | Effect size | CI available? | Function used |
---|---|---|---|
Parametric/Non-parametric | Pearson’s C | Yes | effectsize::pearsons_c() |
Bayesian | No | No | No |
meta_analysis
Hypothesis testing and Effect size estimation
Type | Test | Effect size | CI available? | Function used |
---|---|---|---|---|
Parametric | Meta-analysis via random-effects models | beta | Yes | metafor::metafor() |
Robust | Meta-analysis via robust random-effects models | beta | Yes | metaplus::metaplus() |
Bayes | Meta-analysis via Bayesian random-effects models | beta | Yes | metaBMA::meta_random() |
ggstatsplot
Note that these functions were initially written to display results from statistical tests on ready-made {ggplot2}
plots implemented in {ggstatsplot}
.
For detailed documentation, see the package website: https://indrajeetpatil.github.io/ggstatsplot/
Here is an example from {ggstatsplot}
of what the plots look like when the expressions are displayed in the subtitle-
The hexsticker and the schematic illustration of general workflow were generously designed by Sarah Otterstetter (Max Planck Institute for Human Development, Berlin).
I’m happy to receive bug reports, suggestions, questions, and (most of all) contributions to fix problems and add features. I personally prefer using the GitHub
issues system over trying to reach out to me in other ways (personal e-mail, Twitter, etc.). Pull Requests for contributions are encouraged.
Here are some simple ways in which you can contribute (in the increasing order of commitment):
Read and correct any inconsistencies in the documentation
Raise issues about bugs or wanted features
Review code
Add new functionality (in the form of new plotting functions or helpers for preparing subtitles)
Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms.