Easily make nice per-group QQ plots through
a wrapper around the `ggplot2`

and `qqplotr`

packages.

## Usage

```
nice_qq(
data,
variable,
group,
colours,
groups.labels = NULL,
grid = TRUE,
shapiro = FALSE,
title = variable
)
```

## Arguments

- data
The data frame.

- variable
The dependent variable to be plotted.

- group
The group by which to plot the variable.

- colours
Desired colours for the plot, if desired.

- groups.labels
How to label the groups.

- grid
Logical, whether to keep the default background grid or not. APA style suggests not using a grid in the background, though in this case some may find it useful to more easily estimate the slopes of the different groups.

- shapiro
Logical, whether to include the p-value from the Shapiro-Wilk test on the plot.

- title
An optional title, if desired.

## Value

A qq plot of class ggplot, by group (if provided), along a reference interpretation helper, the 95% confidence band.

## See also

Other functions useful in assumption testing:
`nice_assumptions`

, `nice_density`

,
`nice_normality`

, `nice_var`

,
`nice_varplot`

. Tutorial:
https://rempsyc.remi-theriault.com/articles/assumptions

## Examples

```
# Make the basic plot
nice_qq(
data = iris,
variable = "Sepal.Length",
group = "Species"
)
#> Warning: The following aesthetics were dropped during statistical transformation: sample
#> ℹ This can happen when ggplot fails to infer the correct grouping structure in
#> the data.
#> ℹ Did you forget to specify a `group` aesthetic or to convert a numerical
#> variable into a factor?
#> Warning: The following aesthetics were dropped during statistical transformation: sample
#> ℹ This can happen when ggplot fails to infer the correct grouping structure in
#> the data.
#> ℹ Did you forget to specify a `group` aesthetic or to convert a numerical
#> variable into a factor?
#> Warning: The following aesthetics were dropped during statistical transformation: sample
#> ℹ This can happen when ggplot fails to infer the correct grouping structure in
#> the data.
#> ℹ Did you forget to specify a `group` aesthetic or to convert a numerical
#> variable into a factor?
#> Warning: The following aesthetics were dropped during statistical transformation: sample
#> ℹ This can happen when ggplot fails to infer the correct grouping structure in
#> the data.
#> ℹ Did you forget to specify a `group` aesthetic or to convert a numerical
#> variable into a factor?
#> Warning: The following aesthetics were dropped during statistical transformation: sample
#> ℹ This can happen when ggplot fails to infer the correct grouping structure in
#> the data.
#> ℹ Did you forget to specify a `group` aesthetic or to convert a numerical
#> variable into a factor?
#> Warning: The following aesthetics were dropped during statistical transformation: sample
#> ℹ This can happen when ggplot fails to infer the correct grouping structure in
#> the data.
#> ℹ Did you forget to specify a `group` aesthetic or to convert a numerical
#> variable into a factor?
# Further customization
nice_qq(
data = iris,
variable = "Sepal.Length",
group = "Species",
colours = c("#00BA38", "#619CFF", "#F8766D"),
groups.labels = c("(a) Setosa", "(b) Versicolor", "(c) Virginica"),
grid = FALSE,
shapiro = TRUE,
title = NULL
)
#> Warning: The following aesthetics were dropped during statistical transformation: sample
#> ℹ This can happen when ggplot fails to infer the correct grouping structure in
#> the data.
#> ℹ Did you forget to specify a `group` aesthetic or to convert a numerical
#> variable into a factor?
#> Warning: The following aesthetics were dropped during statistical transformation: sample
#> ℹ This can happen when ggplot fails to infer the correct grouping structure in
#> the data.
#> ℹ Did you forget to specify a `group` aesthetic or to convert a numerical
#> variable into a factor?
#> Warning: The following aesthetics were dropped during statistical transformation: sample
#> ℹ This can happen when ggplot fails to infer the correct grouping structure in
#> the data.
#> ℹ Did you forget to specify a `group` aesthetic or to convert a numerical
#> variable into a factor?
#> Warning: The following aesthetics were dropped during statistical transformation: sample
#> ℹ This can happen when ggplot fails to infer the correct grouping structure in
#> the data.
#> ℹ Did you forget to specify a `group` aesthetic or to convert a numerical
#> variable into a factor?
#> Warning: The following aesthetics were dropped during statistical transformation: sample
#> ℹ This can happen when ggplot fails to infer the correct grouping structure in
#> the data.
#> ℹ Did you forget to specify a `group` aesthetic or to convert a numerical
#> variable into a factor?
#> Warning: The following aesthetics were dropped during statistical transformation: sample
#> ℹ This can happen when ggplot fails to infer the correct grouping structure in
#> the data.
#> ℹ Did you forget to specify a `group` aesthetic or to convert a numerical
#> variable into a factor?
```