temp_drugname = pull(data %>% select(trt) %>% distinct())

library(gtsummary)
library(tidyverse)
my_ratio_summary = function (numerator, na.rm = TRUE, conf.level = 0.95) 
{
  function(data, full_data, ...) {
    temp_drugname = pull(data %>% select(trt) %>% distinct())
    if(length(temp_drugname) > 0){
      druggroup_data = full_data %>% filter(trt == temp_drugname)
    }
    else {
      druggroup_data = full_data
    }
    num <- sum(data[[numerator]], na.rm = na.rm)
    denom <- sum(druggroup_data[[numerator]], na.rm = na.rm)
    ratio <- num/denom
    dplyr::tibble(num = num, denom = denom, ratio = ratio)
  }
}
trial %>%
  filter(!(trt == 'Drug A' & stage == 'T1')) %>%
  tbl_custom_summary(
    include = c("stage"),
    by = "trt",
    stat_fns = ~ my_ratio_summary("response"),
    statistic = ~ "{ratio}%, {num}/{denom}",
    digits = ~ c(style_percent, 0, 0)
  )

<details>
<summary>英文:</summary>
I would like to create a customized gtsummary table, where I have to access the number of cases in that group resulting by `by`.
For example, I would like to calculate the proportion of patients with a response per stage grouped by treatment. 
Currently I use this workaround, to access the treatment group:
    temp_drugname = pull(data%&gt;%select(trt)%&gt;%distinct())
This works only, if there is at least one patient with the current stage in the treatment group.
If there is a stage without patients assigned to it, I can&#39;t find a way to calculate the correct total.
In the example below, I deleted the cases in group A with stage 1 cancer. The total should be 21, not 54, in order to later-on calculate confidence intervals correctly.
[![example with wrong total][1]][1]

dplyr::tibble(num = num, denom = denom, ratio = ratio)

  [1]: https://i.stack.imgur.com/EUcHX.jpg
</details>
# 答案1
**得分**: 0
一个选择是使用通过`...`传递给自定义函数的附加参数，例如第一个元素是一个包含有关当前分组信息的`tibble`，可以用于筛选`full_data`，我使用了`semi_join`。即使`data`不包含任何观察值，这也可以正常工作。
在下面的代码中，我添加了一个`print`语句来显示`...`的内容：
```r
library(gtsummary)
library(tidyverse)
my_ratio_summary <- function(numerator, na.rm = TRUE, conf.level = 0.95) {
  function(data, full_data, ...) {
    
    dots <- list(...)
    
    # 仅添加以打印`dots`的内容
    print(dots)
    
    druggroup_data <- full_data %>% semi_join(dots[[1]], by = dots$by)
    
    num <- sum(data[[numerator]], na.rm = na.rm)
    denom <- sum(druggroup_data[[numerator]], na.rm = na.rm)
    ratio <- num / denom
    dplyr::tibble(num = num, denom = denom, ratio = ratio)
  }
}
trial %>%
  filter(!(trt == "Drug A" & stage == "T1")) %>%
  tbl_custom_summary(
    include = c("stage"),
    by = "trt",
    stat_fns = ~ my_ratio_summary("response"),
    statistic = ~"{ratio}%, {num}/{denom}",
    digits = ~ c(style_percent, 0, 0)
  )

[1]: https://i.stack.imgur.com/yzP0t.png
<details>
<summary>英文:</summary>
One option would be to use the additional arguments passed to the custom function via `...`, e.g. the first element is a `tibble` which contains the info about the current groups which can be used to filter `full_data` for which I use a `semi_join`. This works even if `data` does not contain any observations. 
In the code below I added a `print` statement to show the content of `...`:
``` r
library(gtsummary)
library(tidyverse)
my_ratio_summary &lt;- function(numerator, na.rm = TRUE, conf.level = 0.95) {
  function(data, full_data, ...) {
    
    dots &lt;- list(...)
    
    # Only added to print the content of `dots`
    print(dots)
    
    druggroup_data &lt;- full_data %&gt;% semi_join(dots[[1]], by = dots$by)
    
    num &lt;- sum(data[[numerator]], na.rm = na.rm)
    denom &lt;- sum(druggroup_data[[numerator]], na.rm = na.rm)
    ratio &lt;- num / denom
    dplyr::tibble(num = num, denom = denom, ratio = ratio)
  }
}
trial %&gt;%
  filter(!(trt == &quot;Drug A&quot; &amp; stage == &quot;T1&quot;)) %&gt;%
  tbl_custom_summary(
    include = c(&quot;stage&quot;),
    by = &quot;trt&quot;,
    stat_fns = ~ my_ratio_summary(&quot;response&quot;),
    statistic = ~&quot;{ratio}%, {num}/{denom}&quot;,
    digits = ~ c(style_percent, 0, 0)
  )
#&gt; [[1]]
#&gt; # A tibble: 1 &#215; 2
#&gt;   trt    stage
#&gt;   &lt;chr&gt;  &lt;fct&gt;
#&gt; 1 Drug A T1   
#&gt; 
#&gt; $variable
#&gt; [1] &quot;stage&quot;
#&gt; 
#&gt; $by
#&gt; [1] &quot;trt&quot;
#&gt; 
#&gt; $type
#&gt; [1] &quot;categorical&quot;
#&gt; 
#&gt; $stat_display
#&gt; [1] &quot;{ratio}%, {num}/{denom}&quot;
...