code: func (g *GridType) TickmarksContainY(min, max float64) {
  	g.yTicks, g.yPrecision = Tickmarks(min, max)
  	g.ym, g.yb = linearTickmark(g.yTicks, g.y+g.h, g.y)
  }
docs: // TickmarksContainY sets the tickmarks to be shown by Grid() in the vertical
  // 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 TickmarkExtentY() for an alternative to this method to be used when the
  // exact values of the tickmarks are to be set by the application.