function rangeBand(linear, domain, padding) {
    return (Math.abs(linear(domain.length-1) - linear(0))/Math.max(1, domain.length-1))*(1-padding);
  }
NOTE: The type of tick format returned is dependant on ticks that were generated. To obtain the correct
format for ticks, ensure ticks function is called first, otherwise a default tickFormat will be returned
which may not be the optimal representation of the current domain state.
@returns {Function}