AbstractGridLines and its subclasses are strategy objects that find suitable intervals for plotting grid lines and labels. The data range and warping behavior (e.g. linear or exponential) are derived from the corresponding ControlSpec. The instance methods of AbstractGridLines are used by DrawGrid (which is in turn used by Plotter) for getting logically spaced intervals that span the data for drawing grid lines on a plot.
AbstractGridLines shouldn't be instantiated directly. Instead, the GridLines factory class or the ControlSpec: -grid method should be used to return the appropriate AbstractGridLines subclass for the given spec.
Subclasses of AbstractGridLines correspond to the range and warp behavior of their assigned ControlSpec. For example, LinearGridLines and ExponentialGridLines represent data on a linear and exponential scale, respectively.
This default implementation does not know anything about the data is displaying:
A theoretical MidinoteGridLines could be written that labels these correctly, shows octaves and individual notes depending on the current zoom. Or a DegreeGridLines could draw pitch degree grid lines behind a frequency plot.
Note that the AbstractGridLines does not know which axis it is to be used on and could also be used in polar plots or in 3D rendering.
| spec |
A ControlSpec that defines the numerical range, warp, and step. |
An instance of this class.
AbstractGridLines shouldn't be instantiated directly. Instead, the GridLines factory class or the ControlSpec: -grid method should be used to return the appropriate AbstractGridLines subclass.Return this object.
nil.asGrid returns a BlankGridLines (a subclass of AbstractGridLines) which produces no drawn lines. So if nil is passed to the grid argument of DrawGrid, no lines are drawn on the corresponding axis.
Rounds a value to a logical "nice number" that is within the same order of magnitude. See the discussion below for details.
| val |
The value you'd like to make nicer. |
| round |
A boolean. Roughly speaking, rounding will allow the returned number to be above or below the input val (similar to a |
The nice number.
This method is used to support internal calculations for determining grid line values, though it may be useful for other applications.
Observe the rounding behavior:
The implementation is based on: A. S. Glassner, Ed., Graphics Gems. San Diego: Morgan Kaufmann, 1990.
Returns the logical minimum and maximum that will contain the min and max, determed internally using -niceNum.
| min |
Minimum value to include in the returned range. |
| max |
Maximum value to include in the returned range. |
| ntick |
The number of lines ("ticks") you would like within the range of |
An Array with the lower and upper bounds of the range containing your min and max, i.e. [rangeMin, rangeMax].
Specifically for use by DrawGrid. This returns a Dictionary with keys: 'lines', an array of values where lines should be drawn, and 'labels', an array of 2-element arrays [value, "formatted label"] for each line.
Note that the highest and lowest values returned don't necessarily contain your valueMin and valueMax, but rather represent the values where grid lines will be drawn by DrawGrid (endcap lines are subsequently drawn at the data/grid bounds).
| valueMin |
Minimum value of the data to be plotted. The lowest grid line value returned may be higher than this value. |
| valueMax |
Maximum value of the data to be plotted. The highest grid line value returned may be lower than this value. |
| pixelMin |
Lower bound of the grid's range, in pixels. Used to calculate the size of the available grid space when determining grid values based on tickSpacing (if numTicks is |
| pixelMax |
Upper bound of the grid's range, in pixels. Used to calculate the size of the available grid space when determining grid values based on tickSpacing (if numTicks is |
| numTicks |
Explicit number of ticks you would like to see on the graph (though the result is approximate). Set to |
| tickSpacing |
Minimum distance between ticks (in pixels). This value is only used when numTicks is |
A Dictionary.
Format a numerical value for display as text, rounded to a desired precision.
| val |
The value to round and convert to a text label. |
| numDecimalPlaces |
Number of decimal places to represent in the returned |
A String.