Correlations

library(apa7)
library(dplyr)
library(flextable)
library(ftExtra)
library(tidyr)
library(stringr)

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()

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 bolded instead.

trees |> 
  apa_cor(bold_significant = TRUE)

Table 2. Bolding 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	—
Note. Correlations significant at p < .05 are bolded.

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: FALSE
• star_significant Whether to star significant correlations. Default: TRUE
• 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 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,

# Named list of descriptive functions
my_summaries <- list(Median = median, "Interquartile Range" = IQR)

apa_cor(trees, summary_functions = my_summaries)

Variable		Median	Interquartile Range	1		2		3
1.	Girth	12.90	4.20	—
2.	Height	76.00	8.00	.52	**	—
3.	Volume	24.20	17.90	.97	***	.60	***	—
** p < .01. *** p < .001

# or a vector descriptives
my_summaries <- c("n", "M", "SD", "Skewness", "Kurtosis")

trees |>
  apa_cor(
    p_value = .001,
    digits = 2,
    bold_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	—
Note. Correlations significant at p < .001 are bolded.

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

apa_cor(trees, summary_functions = NA, bold_significant = FALSE)

Variable		1		2		3
1.	Girth	—
2.	Height	.52	**	—
3.	Volume	.97	***	.60	***	—
** p < .01. *** p < .001

Customization

The styling options for apa_cor are minimal, but flextable allows for all kinds of customization. Just place whatever code from flextable you want after apa_cor. 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	***	—
** p < .01. *** p < .001
1This is a footnote.

Output to tibble

If you need to process the underlying data before converting to flextable (or use another table-creating function from another package), you can output a tibble and then process the table however you want. Here we add a row title.

apa_cor(trees, output = "tibble") |>
  mutate(apa7listcolumn = str_trim(apa7listcolumn)) |>
  unite(col = Variable, 
        apa7listcolumn, 
        Variable, 
        sep = " ") |>
  add_row(Variable = "Row title", .before = 1) |>
  apa_flextable(no_format_columns = "Variable") |>
  padding(i = 2:4,
          j = 1,
          padding.left = 15) 

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