Correlations • apa7

library(apa7)
library(dplyr)
library(flextable)
library(ftExtra)

Some tables, like correlation matrices, can be standardized and automated. Others are uniquely tied to a specific purpose, and no function could anticipate their structure. The apa7 package has a few functions to automate what can be automated and a styling function to make the final styling of a complex table a little easier.

By default, the output of apa_cor flextable, with significant correlations bolded.

trees |> 
  apa_cor(star_significant = T)

Table 1. Correlation table using flextable via apa_cor

Variable	M	SD	1		2		3
1. Girth	13.25	3.14	—
2. Height	76.00	6.37	.52	**	—
3. Volume	30.17	16.44	.97	***	.60	***	—
p < .01. * p < .001

Significant correlations can be starred instead.

trees |> 
  apa_cor(star_significant = TRUE)

Table 2. Starring significant correlations

Variable	M	SD	1		2		3
1. Girth	13.25	3.14	—
2. Height	76.00	6.37	.52	**	—
3. Volume	30.17	16.44	.97	***	.60	***	—
p < .01. * p < .001

If you want to use another table package, you can output a tibble instead and then process the table however you want.

options(knitr.kable.NA = '')
trees |> 
  apa_cor(output = "tibble") |> 
  knitr::kable(align = "lrrrrr")

Table 3. Correlation table using kable via apa_cor

Variable	M	SD	1	2	3
1. Girth	13.25	3.14	—
2. Height	76.00	6.37	.52	—
3. Volume	30.17	16.44	.97	.60	—

Styling options

Your styling options include:

note A custom markdown formatted note. Overrides automatic note about bolded correlations being significant. Default: NULL
p_value Significance value. Default: .05
digits Number of digits for rounding. Default: 2
bold_significant Whether to bold significant correlations. Default: TRUE
star_significant Whether to star significant correlations. Default: FALSE
significance_note Whether note about bolding correlations appears. Overridden by a custom note. Also, the automatic note will not appear if no correlations are significant. Default: TRUE
output Options are flextable, gt or tibble. Default: flextable
family Font family (typeface). Default: Times New Roman
font_size Font size (in points). Default: 12
text_color Text color. Default: black
border_color Table border color. Default: black
border_width Table border width. Default: 0.5
line_spacing Text line spacing. Default: 2

For example,

# List of descriptive functions
my_summaries <- list(
                     n = function(x) sum(!is.na(x)),
                     M = mean,
                     SD = sd,
                     Skewness = psych::skew,
                     Kurtosis = psych::kurtosi)
trees |> 
  apa_cor(p_value = .001, 
          digits = 2,
          star_significant = TRUE, 
          significance_note = TRUE,
          summary_functions = my_summaries,
          font_family = "Arial", 
          font_size = 10, 
          text_color = "darkred",
          border_color = "royalblue4", 
          border_width = 1, 
          line_spacing = 2)

Variable	n	M	SD	Skewness	Kurtosis	1		2		3
1. Girth	31	13.25	3.14	0.50	−0.71	—
2. Height	31	76.00	6.37	−0.36	−0.72	.52		—
3. Volume	31	30.17	16.44	1.01	0.25	.97	*	.60	*	—
* p < .001

To remove summary statistics entirely, set summary_functions to NA or NULL.

x <- apa_cor(trees, 
        summary_functions = NA, 
        bold_significant = FALSE)

Customization

The styling options for apa_cor are minimal, but flexable allows for all kinds of customization. Just place whatever code from flextable or gt you want after apa_cor. For example, gt tables usually span 100% of the width in a space. Here I set the width to 50% and align the table to the left of the page. I place a footnote in a specific cell in the table body.

apa_cor(trees) |>
  flextable::footnote(
    i = 2,
    j = "Variable",
    value = flextable::as_paragraph("This is a footnote."),
    part = "body"
  ) |>
  flextable::set_table_properties(
    width = .5, 
    align = "left")

Variable	M	SD	1	2	3
1. Girth	13.25	3.14	—
2. Height1	76.00	6.37	.52	—
3. Volume	30.17	16.44	.97	.60	—
Note. Correlations significant at p < .05 are bolded.
1This is a footnote.