javascript - leaflet / omnivore - create function to display omnivore CSV markers by property value

there seem to be a number of questions out there but none have quite answered this for me.

How would one go about taking a custom set of values from a property like latitude, and then assign them to change the marker color for omnivore.CSV data based on that value. Is there a way of calling the pointtoLayers functions within an onready style section and pointing it to fill colors based on these value tiers?

function getColor(d) {
    return d > 42.2 ? '#800026' :
           d > 39  ? '#BD0026' :

           d > 30  ? '#E31A1C' :
                      '#FFEDA0'; }

var MarkerOptions = {
    radius: 8,
    fillColor: getColor(feature.properties.latitude),
    color: "#000",
    weight: 1,
    opacity: 1,
    fillOpacity: 0.8 };


window.data3 = omnivore.csv('File.csv')
        .on('ready', function(layer) {
            this.eachLayer(function(markeroptions) {

Answer

Welcome to GIS SE!

Note that the Leaflet omnivore plugin API lets you specify more arguments, including a 3rd argument which is an L.GeoJSON layer group that you have prepared before hand.

.csv(url, parser_options?, customLayer?)

In particular, you can set its onEachFeature and/or pointToLayer option(s), so that when omnivore gets the data, it will go through these options.

See: Passing values for a geojson filter in Leaflet

And this Leaflet omnivore example:

var customLayer = L.geoJson(null, {
  // http://leafletjs.com/reference.html#geojson-style
  style: function(feature) {
    return {
      color: '#f00'
    };
  }

});
// this can be any kind of omnivore layer
var runLayer = omnivore.kml('line.kml', null, customLayer)