This vignette is meant for those who wish to contribute to {gtsummary}, or users who wish to gain an understanding of the inner-workings of a {gtsummary} object so they may more easily modify them to suit your own needs. If this does not describe you, please refer to the {gtsummary} website to an introduction on how to use the package’s functions and tutorials on advanced use.
Every {gtsummary} object has a few characteristics common among all objects. Here, we review those characteristics, and provide instructions on how to construct a {gtsummary} object.
Every {gtsummary} object is a list comprising of, at minimum, these elements:
The .$table_body
object is the data frame that will ultimately be printed as the output. The table must include columns "label"
, "row_type"
, and "variable"
. The "label"
column is printed, and the other two are hidden from the final output.
variable | row_type | label | stat_1 | stat_2 |
age | label | Age, yrs | 46 (37, 59) | 48 (39, 56) |
age | missing | Unknown | 7 | 4 |
grade | label | Grade | ||
grade | level | I | 35 (36%) | 33 (32%) |
grade | level | II | 32 (33%) | 36 (35%) |
grade | level | III | 31 (32%) | 33 (32%) |
response | label | Tumor Response | 28 (29%) | 33 (34%) |
response | missing | Unknown | 3 | 4 |
The .$table_header
object is a data frame containing information about each of the columns in .$table_body
(one row per column in .$table_body
). The table header has the following columns:
Column | Description |
---|---|
column | Column name from table_body |
label | Label that will be displayed (if column is displayed in output) |
hide | Logical indicating whether the column is hidden in the output |
align | Specifies the alignment/justification of the column, e.g. ‘center’ or ‘left’ |
missing_emdash | Indicates the rows to include an em-dash for missing cells. For example row_ref == TRUE in tbl_regression() |
indent | String of R code that results in a logical vector that specifies rows to indent, e.g. row_type != 'label' |
text_interpret | the {gt} function that is used to interpret the column label |
bold | For columns that bold rows conditionally, the column includes a string of R code that results in a logical vector indicating the rows to bold For example, row_type == 'label' |
italic | For columns that italicize rows conditionally, the column includes a string of R code that results in a logical vector indicating the rows to italicize. For example, row_type == 'label' |
fmt_fun | If the column needs to be formatted, this list column contains the function that performs the formatting. Note, this is the function object; not the character name of a function. |
footnote_abbrev | Lists the abbreviation footnotes for a table. All abbreviation footnotes are collated into a single footnote. For example, ‘OR = Odds Ratio’ and ‘CI = Confidence Interval’ appear in a single footnote. |
footnote | Lists the footnotes that will appear for each column. |
spanning_header | Includes text printed above columns as spanning headers. See tbl_merge(...)$table_header output for example of use. |
NOTE: Columns ‘hide’, ‘align’, ‘missing_emdash’, ‘indent’, ‘bold’, and ‘italic’ MUST follow the tidyverse style guidelines and include spaces around any variable names, e.g. row_type == 'label'
(NOT row_type=='label'
).
Example from tbl_regression()
column | label | hide | align | missing_emdash | indent | text_interpret | bold | italic | fmt_fun | footnote_abbrev | footnote | spanning_header |
variable | variable | TRUE | center | gt::md | NULL | |||||||
var_type | var_type | TRUE | center | gt::md | NULL | |||||||
row_ref | row_ref | TRUE | center | gt::md | NULL | |||||||
row_type | row_type | TRUE | center | gt::md | NULL | |||||||
label | **Characteristic** | FALSE | left | row_type != 'label' | gt::md | NULL | ||||||
N | N | TRUE | center | gt::md | function (x) ifelse(is.na(x), NA, sprintf("%.0f", x)) | |||||||
estimate | **Beta** | FALSE | center | row_ref == TRUE | gt::md | function (x, digits = 2) { map(digits:1, ~glue("abs(x) < 10^{digits - .x} ~ sprintf('%.{.x}f', x)")) %>% paste(collapse = ", ") %>% { glue("case_when({.}, TRUE ~ ifelse(is.na(x), NA_character_, sprintf('%.0f', x)))") } %>% parse(text = .) %>% eval() %>% { ifelse(as.numeric(.) == 0 & str_starts(., pattern = "-"), str_remove(., pattern = "-"), .) } } | ||||||
conf.low | conf.low | TRUE | center | gt::md | function (x, digits = 2) { map(digits:1, ~glue("abs(x) < 10^{digits - .x} ~ sprintf('%.{.x}f', x)")) %>% paste(collapse = ", ") %>% { glue("case_when({.}, TRUE ~ ifelse(is.na(x), NA_character_, sprintf('%.0f', x)))") } %>% parse(text = .) %>% eval() %>% { ifelse(as.numeric(.) == 0 & str_starts(., pattern = "-"), str_remove(., pattern = "-"), .) } } | |||||||
conf.high | conf.high | TRUE | center | gt::md | function (x, digits = 2) { map(digits:1, ~glue("abs(x) < 10^{digits - .x} ~ sprintf('%.{.x}f', x)")) %>% paste(collapse = ", ") %>% { glue("case_when({.}, TRUE ~ ifelse(is.na(x), NA_character_, sprintf('%.0f', x)))") } %>% parse(text = .) %>% eval() %>% { ifelse(as.numeric(.) == 0 & str_starts(., pattern = "-"), str_remove(., pattern = "-"), .) } } | |||||||
ci | **95% CI** | FALSE | center | row_ref == TRUE | gt::md | NULL | CI = Confidence Interval | |||||
p.value | **p-value** | FALSE | center | gt::md | p.value <= 0.5 | function (x, digits = 1, prepend_p = FALSE) { if (digits == 2) { p_fmt <- case_when(x > 1 ~ NA, x < 0 ~ NA, x > 0.99 ~ ">0.99", round(x, 2) >= 0.1 ~ sprintf("%.2f", x), x >= 0.001 ~ sprintf("%.3f", x), x < 0.001 ~ "<0.001") } else if (digits == 1) { p_fmt <- case_when(x > 1 ~ NA, x < 0 ~ NA, x > 0.9 ~ ">0.9", round(x, 1) >= 0.2 ~ sprintf("%.1f", x), round(x, 2) >= 0.1 ~ sprintf("%.2f", x), x >= 0.001 ~ sprintf("%.3f", x), x < 0.001 ~ "<0.001") } else { stop("'digits' argument must be 1 or 2.") } if (prepend_p == TRUE) { p_fmt <- case_when(is.na(p_fmt) ~ NA, stringr::str_sub(p_fmt, end = 1) %in% c("<", ">") ~ paste0("p", p_fmt), TRUE ~ paste0("p=", p_fmt)) } return(p_fmt) } |
When constructing a {gtsummary} object, the author will begin with the .$table_body
object. Recall the .$table_body
data frame must include columns "label"
, "row_type"
, and "variable"
. Of these columns, only the "label"
column will be printed with the final results. The "row_type"
column typically will control whether or not the label column is indented. The "variable"
column is often used in the inline_text()
family of functions, and merging {gtsummary} tables with tbl_merge()
.
variable | row_type | label |
grade | label | Grade |
grade | level | I |
grade | level | II |
grade | level | III |
marker | label | Marker Level, ng/mL |
The other columns in .$table_body
are created by the user and are likely printed in the output. Formatting and printing instructions for these columns is stored in .$table_header
.
The .$table_header
has one row for every column in .$table_body
containing instructions how to format each column, the column headers, and more. There are a few internal {gtsummary} functions to assist in constructing and modifying a .$table_header
data frame.
First is the table_header_fill_missing()
function. This function ensures .$table_header
contains a row for every column of .$table_body
. If a column does not exist, it is populated with appropriate default values.
gtsummary:::table_header_fill_missing(
table_header = tibble(column = names(tbl_regression_ex$table_body))
)
column | label | hide | align | missing_emdash | indent | text_interpret | bold | italic | fmt_fun | footnote_abbrev | footnote | spanning_header |
variable | variable | TRUE | center | gt::md | NULL | |||||||
var_type | var_type | TRUE | center | gt::md | NULL | |||||||
row_ref | row_ref | TRUE | center | gt::md | NULL | |||||||
row_type | row_type | TRUE | center | gt::md | NULL | |||||||
label | label | TRUE | left | row_type != 'label' | gt::md | NULL | ||||||
N | N | TRUE | center | gt::md | NULL | |||||||
estimate | estimate | TRUE | center | gt::md | NULL | |||||||
conf.low | conf.low | TRUE | center | gt::md | NULL | |||||||
conf.high | conf.high | TRUE | center | gt::md | NULL | |||||||
ci | ci | TRUE | center | gt::md | NULL | |||||||
p.value | p.value | TRUE | center | gt::md | NULL |
The modify_header_internal()
is useful for assigning column headers. The function accepts a complete {gtsummary} object as its input, and returns an updated version where the column labels have been added to .$table_header
. The function also switches the default .$table_header$hide
from TRUE
to FALSE
, resulting in column with labels being printed.
All {gtsummary} objects are printed with print.gtsummary()
. But before a {gtsummary} object is printed, it is converted to a {gt} object using as_gt()
. This function takes the {gtsummary} object as its sole input, and uses the information in .$table_header
to construct a list of {gt} calls that will be executed on .$table_body
. After the {gtsummary} object is converted to {gt}, it is then printed as any other {gt} object.
In some cases, the package defaults to printing with knitr::kable()
utilizing the as_kable()
function.
While the actual print function is slightly more involved, it is basically this: