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Filter Data Prior To Analysis Function

Source: R/filter_df_prior_afun.r
filter_df_prior_afun.Rd

[Experimental]

Applies row filtering to a dataset before executing a user-supplied analysis function.

Usage

filter_df_prior_afun(
  df,
  .var,
  afun,
  subset_expr = expression(rep(TRUE, nrow(df))),
  ...
)

Arguments

df

(data.frame)
data set containing all analysis variables.

.var

(string)
single variable name that is passed by rtables when requested by a statistics function.

afun

(function)
Analysis function. Must accept x or df as its first parameter. Can optionally take other parameters.

subset_expr

(expression or NULL)
Logical expression used to subset rows of df before analysis. Evaluated in the context of df. Defaults to expression(rep(TRUE, nrow(df))), meaning no filtering.

...

Additional arguments passed to afun.

Value

The object returned by afun applied to the filtered dataset.

Details

This is a generic wrapper that:

  1. Subsets df using subset_expr.

  2. Passes data to afun, depending on its first argument. If it is named:

    • x, then df[[.var]] is passed.

    • df, then the df data frame is passed.

  3. Forwards .var (if it is present in the formal arguments of afun) and all additional arguments (...) to afun.

Examples

df <- data.frame(
  USUBJID = rep(1:6, each = 2),
  AVISIT = rep(c("Baseline", "Day 1"), 6),
  AVAL = c(1, 3, 2, 9, 13, 19, 15, 23, 43, 56, 24, 32),
  ABLFL = rep(c(TRUE, FALSE), 6),
  BASE = rep(c(1, 2, 13, 15, 43, 24), each = 2),
  CHG = c(0, 2, 0, 7, 0, 6, 0, 8, 0, 13, 0, 8)
)
df
#>    USUBJID   AVISIT AVAL ABLFL BASE CHG
#> 1        1 Baseline    1  TRUE    1   0
#> 2        1    Day 1    3 FALSE    1   2
#> 3        2 Baseline    2  TRUE    2   0
#> 4        2    Day 1    9 FALSE    2   7
#> 5        3 Baseline   13  TRUE   13   0
#> 6        3    Day 1   19 FALSE   13   6
#> 7        4 Baseline   15  TRUE   15   0
#> 8        4    Day 1   23 FALSE   15   8
#> 9        5 Baseline   43  TRUE   43   0
#> 10       5    Day 1   56 FALSE   43  13
#> 11       6 Baseline   24  TRUE   24   0
#> 12       6    Day 1   32 FALSE   24   8

afun <- tern::a_summary
.stats <- c("n", "mean_sd")

# No filtering.
filter_df_prior_afun(df, "CHG", afun, .stats = .stats)
#> RowsVerticalSection (in_rows) object print method:
#> ----------------------------
#>   row_name formatted_cell indent_mod row_label
#> 1        n             12          0         n
#> 2  mean_sd      3.7 (4.5)          0 Mean (SD)

# Baseline records only.
filter_df_prior_afun(df, "CHG", afun, expression(ABLFL), .stats = .stats)
#> RowsVerticalSection (in_rows) object print method:
#> ----------------------------
#>   row_name formatted_cell indent_mod row_label
#> 1        n              6          0         n
#> 2  mean_sd      0.0 (0.0)          0 Mean (SD)