Post-Processing

String wrapping

Certain types of output formats don’t elegantly handle string wrapping of text. For some formats, this could simply be the width of the text before a word wraps. Other formats, such as LaTex outputs to PDF (depending on the rendering engine) may wrap white space fine, but words whose character length is longer than the allotted width may print wider than the table cell.

To address this, in Tplyr we’ve added the function str_indent_wrap(). This is largely built on top of the function stringr::str_wrap() to preserve as much efficiency as possible, but two issues common in clinical outputs have been addressed:

• Preceding indentation of a word is preserved. So for example, in a nested adverse event table, if the preferred term is indented, this function will wrap but preserve that words indentation with each new line.
• Words that exceed the specified width will be wrapped with hyphenation.

As a post-processing function, note that this function works on a tibble or data.frame object, and not a Tplyr table.

Let’s look at an example.

dat <- tibble(
  row_label1 = c("RENAL AND URINARY DISORDERS", "   NEPHROLITHIASIS"),
  var1_Placebo = c(" 5 (50.0%)", " 3 (30.0%)")
)

dat %>% 
  mutate(
    row_label1 = str_indent_wrap(row_label1, width = 10)
  )
#> # A tibble: 2 × 2
#>   row_label1                      var1_Placebo
#>   <chr>                           <chr>       
#> 1 "RENAL AND\nURINARY\nDISORDERS" " 5 (50.0%)"
#> 2 "   NEPHROLIT-\n   HIASIS"      " 3 (30.0%)"

Note: We’re viewing the data frame output here because HTML based outputs eliminate duplicate white spaces, which makes it difficult to see things like padded indentation

Row Masking

Row masking is the process blanking of repeat row values within a data frame to give the appearance of grouping variables. Some table packages, such as gt, will handle this for you. Other packages, like huxtable, have options like merging cells, but this may be a more simplistic approach. Furthermore, this is a common approach in clinical tables when data validation is done on an output dataframe.

dat <- tplyr_table(adsl, TRT01P) %>% 
  add_layer(
    group_count(RACE, by = "Race n (%)")
  ) %>% 
  build() %>% 
  select(1:3)

kable(dat)

In this example, note that “Race n (%)” is duplicated for each row. We can blank this out using `apply_row_masks()

dat %>% 
  apply_row_masks() %>% 
  kable()

A second feature of apply_row_masks() is the ability to apply row breaks between different groups of data, for example, different layers of a table.

dat <- tplyr_table(adsl, TRT01P) %>% 
  add_layer(
    group_count(RACE, by = "Race n (%)")
  ) %>% 
  add_layer(
    group_desc(AGE, by = "Age (years)")
  ) %>% 
  build()
  
dat %>% 
  apply_row_masks(row_breaks=TRUE) %>% 
  kable()

The row breaks are inserted as blank rows. Additionally, when row breaks are inserted you’ll have the additional variable ord_break added to the dataframe, where the value is 1 for table data rows and 2 for the newly added break rows. Character variables will have blank values (i.e. "") and the numeric sorting values will be NA.

There are a few considerations when using apply_row_masks():

• This function is order dependent, so make sure your data are sorted before submitting to apply_row_masks()
• When inserting row breaks, by default the Tpylr variable ord_layer_index is used. You can submit other variables via the ellipsis parameter (...) if you’d like to use a different variable grouping to insert rows

Conditional Formatting

In some circumstances, like add_total_row(), Tplyr lets you specify special formats separate from those in set_format_strings(). But within the table body there’s no other way to set specific, conditional formats based on the table data itself. To address this, we’ve added the post-processing function apply_conditional_format() to allow you to set conditional formats on result cells.

apply_conditional_format() operates on a character vector, so it can generally be used within the context of dplyr::mutate() like any other character modifying function. It will make a 1:1 replacement of values, so it will return a character vector of equal length. Let’s look at two examples.

string <- c(" 0  (0.0%)", " 8  (9.3%)", "78 (90.7%)")

apply_conditional_format(string, 2, x == 0, " 0        ", full_string=TRUE)
#> [1] " 0        " " 8  (9.3%)" "78 (90.7%)"

apply_conditional_format(string, 2, x == 0, "")
#> [1] " 0        " " 8  (9.3%)" "78 (90.7%)"

The two examples above achieve the same result, but they work slightly differently. Let’s walk throug the syntax:

• The first parameter is the input character vector
• The second parameter refers to the format group. The format group is the index of the number within the result cell you’d like to target. So in the result 8 (9.3%), there are two format groups. The value of the first is 8. The value of the second is 9.3. This controls the number that we’ll use to establish our condition.
• The third parameter is the condition that will evaluate to establish if the conditional format is applied. Here, use the variable name x, which takes on the value of the from your chosen format group. This condition should be a filter condition, so it must return a boolean vector of TRUE/FALSE.
• The fourth parameter is the string value used as your replacement.

Finally, the last parameter is full_string, and this is the difference between the first and second examples. apply_conditional_format() can do two types of replacements. The first example is a full string replacement. In this case, whatever value you provide as the replacement is used verbatim when the condition evaluates to TRUE. If this is set to false, the only the format group specified is replaced. For more context, let’s look at a third example.

apply_conditional_format(string, 2, x < 1, "(<1%)")
#> [1] " 0   (<1%)" " 8  (9.3%)" "78 (90.7%)"

In this example we target the percent field using format group 2, and now our replacement text is (<1%). If full_string uses its default value of FALSE, only the format group specified is replaced. apply_conditional_format() establishes the width of the format group targeted, and the replacement text will right align within that targetted portion of the string to ensure that the alignment of the string is preserved.

For any example within a Tplyr result dataframe, let’s look at the example dataset from earlier. Let’s say that we have n (%) values within the first count layer to conditional format. Using some fancy dplyr code, and apply_conditional_format(), we can make it happen.

dat_new <- dat %>% 
  mutate(
    across(starts_with('var'),  # Apply to variables that start with `var`
    ~ if_else(
      ord_layer_index == 1,     # Target the count layer
      apply_conditional_format( 
        string = .,             # This is dplyr::across syntax
        format_group = 2,       # The percent field
        condition = x == 0,     # Our condition
        replacement = ""        # Replacement value
      ),
      .
      )
    )
  )

kable(dat_new)

The syntax here gets a bit complicated, by using dplyr::across() we can apply the same function across each of the result variables, which in this the variable names start with var. The function here is using a purrr style anonymous function for simplicity. There are a couple ways you can do this in R. Referencing the documentation of purrr::map():

• A formula, e.g. ~ . + 1. You must use . to refer to the first argument. Only recommended if you require backward compatibility with older versions of R.
• An anonymous function, e.g. \(x) x + 1 or function(x) x + 1.

Within that function, we’re additionally using if_else() to only apply this function on the first layer by using the ord_layer_index variable. All this together, we’re effectively running the apply_conditional_formats() function only on the first layer, and running it across all of the variables that start with var.

Extracting a Format Group

When Tplyr outputs a result, using set_format_strings() and f_str() the result are concatenated together within a single result cell. For example, within a count layer in a Tplyr table, there’s no way to directly output the n and pct values in separate columns. If this is a result you want, then in a post-processing step you can use the function str_extract_fmt_group().

str_extract_fmt_group() allows you to reach within a result string and extract an individual format group. Consider this example:

string <- c(" 5  (5.8%)", " 8  (9.3%)", "78 (90.7%)")

# Get the n counts
str_extract_fmt_group(string, 1)
#> [1] " 5" " 8" "78"

# Get the pct counts
str_extract_fmt_group(string, 2)
#> [1] "(5.8%)"  "(9.3%)"  "(90.7%)"

In the first call to str_extract_fmt_group(), we target the n counts. The first format group from each string is extracted, preserving the allotted width of that portion of the string. Similarly, in the second group we extract all the percent counts, including the surround parentheses.

In practice, str_extract_fmt_group() can then be used to separate format groups into their own columns.

dat <- tplyr_table(adsl, TRT01P) %>% 
  add_layer(
    group_count(RACE)
  ) %>% 
  build()

dat %>% 
  mutate(
    across(starts_with('var'), 
           ~ str_extract_fmt_group(., 1),
           .names = "{.col}_n"),
    across(starts_with('var'), 
           ~ str_extract_fmt_group(., 2),
           .names = "{.col}_pct")
  ) %>% 
  select(row_label1, var1_Placebo_n, var1_Placebo_pct) %>% 
  kable()

For the sake of display, in this output I only select the Placebo column, but note that we were able to dynamically separate out the n results from the pct results. In some cases, functions such as tidyr::separate() could also be used to get a result like this, but str_extract_fmt_group() specifically targets the expected formatting of format groups, without having to craft a specific expression that may get confused over things like spaces in unexpected places.

Highly Customized Sort Variables

In very much the same vein as str_extract_fmt_group(), the function str_extract_num() allows you to target a format group and extract the number from within. This can be used in any circumstance where you may want to pull a number out of a result cell, but probably the best example of this would be for a highly specific sort sequence.

Consider an adverse event table. In vignette("sort") we go over circumstances where you may want to sort by the descending occurrence of a result. We’ve received questions about how to establish tie breakers in this scenario, where ties should be broken sorting descending occurrence of an adverse event within the high dose group, then the low dose group, and finally the placebo group. Tplyr doesn’t allow you to output these order variables by default, but getting these numbers is quite simple with str_extract_num(). Let’s consider a simplified scenario

dat <- tplyr_table(adae, TRTA) %>% 
  set_pop_data(adsl) %>% 
  set_pop_treat_var(TRT01A) %>% 
  add_layer(
    group_count(AEDECOD) %>% 
      set_format_strings(f_str("xx (XX.x%) [A]", distinct_n, distinct_pct, n))  %>% 
      set_distinct_by(USUBJID)
  ) %>% 
  build()

dat %>% 
  head() %>% 
  kable()

Given this data, let’s say we want to sort by descending occurrence of the event, using the number of subjects. That would be the first format group. And then we want to sort using high dose, then low dose, then placebo. Let’s create the order variables.

dat_ord <- dat  %>% 
  mutate(
    across(starts_with('var1'),
           ~str_extract_num(., 1),
           .names = "{.col}_ord")
  ) 

dat_ord %>% 
  head() %>% 
  select(row_label1, matches('^var.*ord$'))
#> # A tibble: 6 × 4
#>   row_label1         var1_Placebo_ord `var1_Xanomeline High Dose_ord` var1_Xan…¹
#>   <chr>                         <dbl>                           <dbl>      <dbl>
#> 1 ACTINIC KERATOSIS                 0                               1          0
#> 2 ALOPECIA                          1                               0          0
#> 3 BLISTER                           0                               1          5
#> 4 COLD SWEAT                        1                               0          0
#> 5 DERMATITIS ATOPIC                 1                               0          0
#> 6 DERMATITIS CONTACT                0                               0          1
#> # … with abbreviated variable name ¹​`var1_Xanomeline Low Dose_ord`

Now we effectively have additional order variables necessary to do the sort sequence desired.

External Data Formatting

The last post processing function worth mentioning isn’t necessarily meant for post-processing data from Tplyr itself. We understand that Tplyr can’t produce every single summary you’d need for a clinical trial - and we never intended it to be able to do this. But we built Tplyr to try to work effectively with other packages and tools. Tplyr’s string formatting tools work quite well, so we’ve externalized this capability using the function apply_formats().

As a basic example, let’s look at the mtcars data.

mtcars %>% 
  mutate(
    new_column = apply_formats("xx (xx.x)", gear, mpg)
  ) %>% 
  select(gear, mpg, new_column) %>% 
  head() %>% 
  kable()

Here we were able to leverage the string formatting available in f_str(), but apply it generically in another data frame within dplyr::mutate(). This allows you to format other data, outside of Tplyr, but still bring some of the quality of life that Tplyr has to offer.