function getNumElementsFromNonIndexedArrays(arrays) {
	    var key;
	    for (var ii = 0; ii < positionKeys.length; ++ii) {
	      key = positionKeys[ii];
	      if (key in arrays) {
	        break;
	      }
	    }
	    if (ii === positionKeys.length) {
	      key = Object.keys(arrays)[0];
	    }
	    var array = arrays[key];
	    var length = getArray(array).length;
	    var numComponents = getNumComponents(array, key);
	    var numElements = length / numComponents;
	    if (length % numComponents > 0) {
	      throw "numComponents " + numComponents + " not correct for length " + length;
	    }
	    return numElements;
	  }
tries to get the number of elements from a set of arrays.