
  For the last 6-8 month I made barely any progress (lots of failed
  experiments)


This sounds like you have not treated your prelims as a contract negotiation. 

The best advice I've received is that when you pitch your thesis topic to the committee, make sure that everyone agrees on the structure and methodologies involved. That way, if your work falters or your experiments fail, but you followed the guidance outlined by your committee, then you have still earned a pass.

Another piece of great advice is this: nobody is going to read your thesis. 

Do not switch your program and do not start over, just complete the tasks you were given and move on. If you decide to switch fields later on, fine... that's normal, reasonable, and expected.

And just because you're studying one thing in school doesn't mean that's what you have to do for the rest of your life. There have been plenty of PhDs that completely jumped fields of study, out of CS and into sociology for example... or vice versa. Besides, the latest rage these days is adding "multi-disciplinary" to your grant proposals.

Changing PhD topic and effect on career
I am new to mapbox and I have a simple question. I have made a feature layer and a list of custom icons. How do I add the two together?

My feature layer is formatted as below:

L.mapbox.featureLayer({
     "type": "Feature",
     "geometry": {
     "coordinates": [
     '.$long.','.$lat.'
     ],
     "type": "Point"
     },
     "properties": {
     "title": "'.$business_name.'",
     "description": "'.$address_1.', '.$address_2.', '.$address_3 .', '.$postcode .'"
     }
     }).addTo(map);


And example of my custom marker is below

var accomodation = L.icon({
    iconUrl: '/img/pins/day-and-night/accommodation.png',
    iconSize: [46, 62],
    iconAnchor: [8, 60],
    });


Any help would be perfect.

Thanks
