code: func (g *GridType) TickmarksContainX(min, max float64) {
  	g.xTicks, g.xPrecision = Tickmarks(min, max)
  	g.xm, g.xb = linearTickmark(g.xTicks, g.x, g.x+g.w)
  }
docs: // TickmarksContainX sets the tickmarks to be shown by Grid() in the horizontal
  // dimension. The argument min and max specify the minimum and maximum values
  // to be contained within the grid. The tickmark values that are generated are
  // suitable for general purpose graphs.
  //
  // See TickmarkExtentX() for an alternative to this method to be used when the
  // exact values of the tickmarks are to be set by the application.