title: Function to calculate geospatial distance between two points (lat,long) using R
body: <p>I have geocoded points in long, lat format, and I want to calculate the distance between them using R.  This seems pretty straight forward, yet I can't find a function that will do it easily.  I've been attempting to do it with the gdistance package, but it seems very convoluted and oriented to graphing, I just need a number.  Something like <code>distanceBetween(pointA,pointB)</code> that returns a number.  </p>