Summarize the ratio of two variables — ratio

This helper, to be used with tbl_custom_summary(), creates a function computing the ratio of two continuous variables and its confidence interval.

ratio_summary(numerator, denominator, na.rm = TRUE, conf.level = 0.95)

Arguments

numerator: (string)
String indicating the name of the variable to be summed for computing the numerator.
denominator: (string)
String indicating the name of the variable to be summed for computing the denominator.
na.rm: (scalar logical)
Should missing values be removed before summing the numerator and the denominator? (default is TRUE)
conf.level: (scalar numeric)
Confidence level for the returned confidence interval. Must be strictly greater than 0 and less than 1. Default to 0.95, which corresponds to a 95 percent confidence interval.

Details

Computed statistics:

{num} sum of the variable defined by numerator
{denom} sum of the variable defined by denominator
{ratio} ratio of num by denom
{conf.low} lower confidence interval
{conf.high} upper confidence interval

Confidence interval is computed with stats::poisson.test(), if and only if num is an integer.

Author

Joseph Larmarange

Examples

# Example 1 ----------------------------------
trial |>
  tbl_custom_summary(
    include = c("stage", "grade"),
    by = "trt",
    stat_fns = ~ ratio_summary("response", "ttdeath"),
    statistic = ~"{ratio} [{conf.low}; {conf.high}] ({num}/{denom})",
    digits = ~ c(ratio = 3, conf.low = 2, conf.high = 2),
    overall_row = TRUE,
    overall_row_label = "All stages & grades"
  ) |>
  bold_labels() |>
  modify_footnote_header("Ratio [95% CI] (n/N)", columns = all_stat_cols())


  Characteristic
      Drug A

N = 98¹
      Drug B

N = 102¹
    
All stages & grades
0.014 [0.01; 0.02] (28.0000/1,983.0000)
0.017 [0.01; 0.02] (33.0000/1,941.6100)
T Stage



    T1
0.012 [0.00; 0.02] (7/583)
0.021 [0.01; 0.04] (11/522)
    T2
0.011 [0.00; 0.02] (6/528)
0.012 [0.01; 0.03] (7/560)
    T3
0.019 [0.01; 0.04] (8/426)
0.016 [0.01; 0.03] (7/425)
    T4
0.016 [0.01; 0.03] (7/445)
0.018 [0.01; 0.04] (8/434)
Grade



    I
0.011 [0.00; 0.02] (8/734)
0.019 [0.01; 0.03] (13/690)
    II
0.011 [0.00; 0.02] (7/651)
0.019 [0.01; 0.03] (12/645)
    III
0.022 [0.01; 0.04] (13/598)
0.013 [0.01; 0.03] (8/607)
¹ Ratio [95% CI] (n/N)

Characteristic	Drug A N = 98¹	Drug B N = 102¹
All stages & grades	0.014 [0.01; 0.02] (28.0000/1,983.0000)	0.017 [0.01; 0.02] (33.0000/1,941.6100)
T Stage
T1	0.012 [0.00; 0.02] (7/583)	0.021 [0.01; 0.04] (11/522)
T2	0.011 [0.00; 0.02] (6/528)	0.012 [0.01; 0.03] (7/560)
T3	0.019 [0.01; 0.04] (8/426)	0.016 [0.01; 0.03] (7/425)
T4	0.016 [0.01; 0.03] (7/445)	0.018 [0.01; 0.04] (8/434)
Grade
I	0.011 [0.00; 0.02] (8/734)	0.019 [0.01; 0.03] (13/690)
II	0.011 [0.00; 0.02] (7/651)	0.019 [0.01; 0.03] (12/645)
III	0.022 [0.01; 0.04] (13/598)	0.013 [0.01; 0.03] (8/607)
¹ Ratio [95% CI] (n/N)