Generate Sankey data for Google Sheets with this custom formula

gistfile1.js

function setSankey(data, cols, optSplit) {
  // data - is all columns of the the response data minus the header e.g. 'Form Responses'!A2:P
  // cols - string of comma seperated column letters
  var splitBy = optSplit || ", ";
  var output = [["source","target","value"]];
  var edges = {};
  var cols = cols.split(",");
  for (i in cols){
    cols[i] = charToCol(cols[i].trim().toUpperCase()); 
  }
  for (var c = 0; c <  cols.length-1; c++){
    for (i in data){
      var sources = data[i][cols[c]].split(splitBy);
      for (s in sources){
        if (sources[s] !=""){
          var targets = data[i][cols[c+1]].split(splitBy);
          for (t in targets){
            if (targets[t] !=""){
              if (edges[sources[s]+"|"+targets[t]] == undefined){
                edges[sources[s]+"|"+targets[t]] = {source:sources[s],
                                                    target: targets[t],
                                                    value: 1};
              } else {
                edges[sources[s]+"|"+targets[t]].value = edges[sources[s]+"|"+targets[t]].value+1;
              }
            }
          }
        }
      }
    }
  }
  for (i in edges){
    output.push([edges[i].source,edges[i].target,edges[i].value]);
  }              
  return output;
}

// http://stackoverflow.com/a/9906193/1027723
function charToCol(val) {
  var base = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', i, j, result = 0;
  for (i = 0, j = val.length - 1; i < val.length; i += 1, j -= 1) {
    result += Math.pow(base.length, j) * (base.indexOf(val[i]) + 1);
  }
  return result-1;
};