We've identified two key issues:

d[",nested_columns,"]['cohort'].length

The problem here lies in the absence of a cohort column. It should be replaced with:

d[",nested_columns,"]['studyName'].length

Additionally, there's an issue with replacing dots with underscores:

var result = ('<table id=\"child_' + ",not_nested_columns_str," + '\">').replace('.','_') + '<thead><tr>'

This code snippet only replaces the first dot encountered. To address this, modify it to:

var result = ('<table id=\"child_' + ",not_nested_columns_str," + '\">').replace('/\\./g','_') + '<thead><tr>'

A similar correction is needed here as well:

var subtable = $(('table#child_' + ",not_nested_columns_str,").replace('.','_')).DataTable({

https://i.sstatic.net/Z9H95.gif

Complete code snippet for context:

library(DT)
library(tidyr)
library(dplyr)
library(tibble)

# Establish dataframe for summarizing results
allresults <- list(c("HeartAttack", 1e-6, 0.05, 0.005, "study1", "heartAttack_v1", "ageSex", 1e-6), 
                   c("HeartAttack", 1e-6, 0.05, 0.005, "study1", "heartAttack_v2", "ageSexBmi", 0.001), 
                   c("HeartAttack", 1e-6, 0.05, 0.005, "study2", "heartAttack_v1", "ageSex", 0.05), 
                   c("HeartAttack", 1e-6, 0.05, 0.005, "study2", "heartAttack_v2", "ageSexBmi", "0.2"), 
                   c("HeartAttack", 1e-6, 0.05, 0.005, "study3", "heartAttack_v1", "ageSex", "0.005"), 
                   c( "Cancer",  0.05, 0.01, 0.002, "study1", "cancer_v1", "ageSex", 0.6), 
                   c( "Cancer",  0.05, 0.01, 0.002, "study1", "cancer_v2", "ageSex", 0.05), 
                   c("Cancer",  0.05, 0.01, 0.002, "study2", "cancer_v1", "ageSexBmi", 0.2), 
                   c("Cancer",  0.05, 0.01, 0.002, "study2", "cancer_v2", "ageSex", 0.01), 
                   c("Cancer",  0.05, 0.01, 0.002, "study3", "cancer_v1", "ageSexBmi", 0.002))

df <- as.data.frame(t(as.data.frame(allresults)))
colnames(df) <- c("outcome.bestOf", "study1.bestOf", "study2.bestOf", "study3.bestOf", "studyName", "outcome", "model", "pvalue")
rownames(df)<-NULL

# Collapse data for displaying top-result table with one row per outcome
nest_fields <- c("outcome.bestOf", "study1.bestOf", "study2.bestOf", "study3.bestOf") 
dt <- df %>%
  nest(-nest_fields)

# Add (+) column
data <- dt %>% {bind_cols(data_frame(' ' = rep('&oplus;',nrow(.))),.)}

# Access dynamic info and strings
# Source: https://github.com/rstudio/shiny-examples/issues/9

nested_columns         <- which(sapply(data,class)=="list") %>% setNames(NULL)
not_nested_columns     <- which(!(seq_along(data) %in% c(1,nested_columns)))
not_nested_columns_str <- not_nested_columns %>% paste(collapse="] + '_' + d[") %>% paste0("d[",.,"]")

# Callback function
callback <- paste0("
                   table.column(1).nodes().to$().css({cursor: 'pointer'});

                   // Convert nested table into formatted content
                   var format = function(d) {
                   if(d != null){ 
                   var result = ('<table id=\"child_' + ",not_nested_columns_str," + '\">').replace(/\\./g,'_') + '<thead><tr>'
                   for (var col in d[",nested_columns,"]){
                   result += '<th>' + col + '</th>'
                   }
                   result += '</tr></thead></table>'
                   return result
                   }else{
                   return '';
                   }
                   }

                   var format_datatable = function(d) {
                   var dataset = [];
                   for (var i = 0; i < + d[",nested_columns,"]['studyName'].length; i++) {
                   var datarow = [];
                   for (var col in d[",nested_columns,"]){
                   datarow.push(d[",nested_columns,"][col][i])
                   }
                   dataset.push(datarow)
                   }
                   var subtable = $(('table#child_' + ",not_nested_columns_str,").replace(/\\./g,'_')).DataTable({
                   'data': dataset,
                    'autoWidth': true, 
                      'deferRender': true, 
                      'info': false, 
                      'lengthChange': false, 
                      'ordering': true, 
                      'paging': false, 
                      'scrollX': false, 
                      'scrollY': false, 
                      'searching': false 
                   });
                   };

                   table.on('click', 'td.details-control', function() {
                   var td = $(this), row = table.row(td.closest('tr'));
                   if (row.child.isShown()) {
                   row.child.hide();
                   td.html('&oplus;');
                   } else {
                   row.child(format(row.data())).show();
                   td.html('&CircleMinus;');
                   format_datatable(row.data())
                   }
                   });"
                  )


# Display DataTable
datatable(
  data,
  escape = FALSE,
  options = list(
    columnDefs = list(
      list(visible = FALSE, targets = c(0,nested_columns) ), # Hide row numbers and nested columns
      list(orderable = FALSE, className = 'details-control', targets = 1) # turn first column into control column
    )
  ),
  callback = JS(callback)
)