Change Marker Opacity In A Scatter Chart

//Series you want to adjust. Leaving this array empty will adjust all series in he chart.
var categoriesToChange = []; 
//Opacity value between 0 (completely transparent) and 1 (completely solid)
var opacity = 0.1;


widget.on('beforeviewloaded',function(se,ev){
 
 
 // if the array is empty, change opacity for all categories
 if(categoriesToChange.length === 0){
   ev.options.series.forEach(function(ser){
     if (ser.marker){
       ser.marker.fillOpacity = opacity;
     }
   })
 }
 else {
   categoriesToChange.forEach(function(category){
   
   var ser = ev.options.series.find(function(s){ 
     return s.name.toLowerCase() === category.toLowerCase();} 
   ); 
   if (ser.marker){
     ser.marker.fillOpacity = opacity;
   }
 })
 
 }
})