# Graduated Panels

The "Graduated" Panel, Panel,Graduated, draws regular tick marks and/or text labels along the stroke of the main child Shape. Graduated Panels can be considered scales showing a range of values.

For examples of Graduated Panels see the Timeline, Thermometer, Instrument Gauge, and Rulered Diagram samples.

## Simple Graduated Panels

Similar to Auto and Spot Panels, Graduated Panels should have two or more elements in them. Elements must be either Shapes or TextBlocks. The main Shape element may be declared by setting GraphObject.isPanelMain to true; but no such setting is needed if it is the very first element of the panel. Shapes and TextBlocks, other than the main Shape, basically act as templates for the drawing of each tick mark and label.

Tick mark Shapes within a Graduated Panel should have a measured size, either by setting a GraphObject.desiredSize (or `width` and `height` properties), or by setting its Shape.geometry. For basic tick marks drawn normal to the main Shape's path, it is easiest to use a simple vertical line geometry string: `M0 0 V10`. The height of the geometry will determine the length of the tick mark.

    diagram.add(
      // all Parts are Panels
      $(go.Part, go.Panel.Graduated,  // or "Graduated"
        $(go.Shape, { geometryString: "M0 0 H400" }),  // the main shape, a horizontal line
        $(go.Shape, { geometryString: "M0 0 V10" })  // a tick mark, a vertical line
      ));

Any shape, including custom geometries, can be used as the main Shape or as a tick mark Shape of a Graduated Panel.

    diagram.add(
      $(go.Part, "Graduated",
        { background: "transparent" }, // make panel pickable
        // main shape is a whole circle
        $(go.Shape, "Circle",
          { fill: null, desiredSize: new go.Size(150, 150) }),
        // tick shape is a double line
        $(go.Shape, { geometryString: "M0 0 V10 M3 0 V10" })
      ));

Graduated Panels can also be labeled with TextBlocks denoting the values along the scale. Often, these will be offset from the main stroke using GraphObject.segmentOffset, as one would with Link labels, so that the text does not overlap the main stroke. More detail on placing labels is in the "Appearance" section below.

    diagram.add(
      $(go.Part, "Graduated",
        { background: "transparent" }, // make panel pickable
        $(go.Shape, { geometryString: "M0 0 H400" }),  // the main shape
        $(go.TextBlock, { segmentOffset: new go.Point(0, 12) })  // tick labels
      ));

## Graduated Panel Properties

There are a number of properties that govern the appearance of tick marks and labels.

### Tick Mark Values

The graduated values of a Graduated Panel will range on a linear scale from the start of the main shape's stroke to the end of the stroke. The values and frequency of tick marks and labels are governed by a few properties:

- Panel.graduatedMin - the minimum value represented on the scale, at the beginning of the stroke of the main shape
- Panel.graduatedMax - the maximum value represented on the scale, at the end of the main shape
- Panel.graduatedTickBase - the value of the "origin" tick mark, the first tick mark if it is the same as graduatedMin
- Panel.graduatedTickUnit - tick marks are positioned at multiples of the graduatedTickUnit added to the graduatedTickBase
- Shape.interval/TextBlock.interval - a multiple of the graduatedTickUnit at which to draw a tick or label

Graduated Panels can have multiple Shapes as tick marks and multiple TextBlocks as labels, with the interval property controlling at what multiples of the `graduatedTickUnit` they are drawn. In many of the examples below, larger ticks are drawn at intervals of 4; some have an interval of 5.

A `graduatedMin` of `0`, `graduatedMax` of `77`, `graduatedTickBase` of `0`, `graduatedTickUnit` of `2.5`, and intervals of 4 result in a scale that might appear as:

    diagram.add(
      $(go.Part, "Graduated",
        {
          graduatedMin: 0, graduatedMax: 77,
          graduatedTickBase: 0, graduatedTickUnit: 2.5,
          background: "transparent"
        },
        $(go.Shape, { geometryString: "M0 0 H400" }),  // the main Shape
        // a short, frequent tick mark
        $(go.Shape, { geometryString: "M0 0 V5" }),
        // a longer tick mark every four ticks
        $(go.Shape, { geometryString: "M0 0 V10", interval: 4 }),
        // text label only every four ticks, with a vertical offset
        $(go.TextBlock, { segmentOffset: new go.Point(0, 12), interval: 4 })
      ));

Changing `graduatedMin` to `-23` results in:

    diagram.add(
      $(go.Part, "Graduated",
        {
          graduatedMin: -23, graduatedMax: 77,
          graduatedTickBase: 0, graduatedTickUnit: 2.5,
          background: "transparent"
        },
        $(go.Shape, { geometryString: "M0 0 H400" }),  // the main Shape
        $(go.Shape, { geometryString: "M0 0 V5" }),  // short tick mark
        $(go.Shape, { geometryString: "M0 0 V10", interval: 4 }),  // long tick mark
        $(go.TextBlock, { segmentOffset: new go.Point(0, 12), interval: 4 })  // labels
      ));

The range from the min to the max value (Panel.graduatedRange) has increased from 77 to 100, so the tick marks are closer to each other for the same length main path.

Changing `graduatedTickBase` to `1.2` results in:

    diagram.add(
      $(go.Part, "Graduated",
        {
          graduatedMin: -23, graduatedMax: 77,
          graduatedTickBase: 1.2, graduatedTickUnit: 2.5,
          background: "transparent"
        },
        $(go.Shape, { geometryString: "M0 0 H400" }),  // the main Shape
        $(go.Shape, { geometryString: "M0 0 V5" }),  // short tick mark
        $(go.Shape, { geometryString: "M0 0 V10", interval: 4 }),  // long tick mark
        $(go.TextBlock, { segmentOffset: new go.Point(0, 12), interval: 4 })  // labels
      ));

Basically, the "origin" for the scale has shifted slightly, even though the end values remain the same. There will always be a tick mark at the `graduatedTickBase` if that value is within the range of the graduated scale.

Doubling the `graduatedTickUnit` to `5` results in:

    diagram.add(
      $(go.Part, "Graduated",
        {
          graduatedMin: -23, graduatedMax: 77,
          graduatedTickBase: 1.2, graduatedTickUnit: 5,
          background: "transparent"
        },
        $(go.Shape, { geometryString: "M0 0 H400" }),
        $(go.Shape, { geometryString: "M0 0 V5" }),  // short tick mark
        $(go.Shape, { geometryString: "M0 0 V10", interval: 4 }),  // long tick mark
        $(go.TextBlock, { segmentOffset: new go.Point(0, 12), interval: 4 })  // labels
      ));

Doubling the tick unit halves the number of ticks for the same length path, but again the end values are unchanged.

Changing `graduatedTickBase` back to `0` and the intervals to `5` results in:

    diagram.add(
      $(go.Part, "Graduated",
        {
          graduatedMin: -23, graduatedMax: 77,
          graduatedTickBase: 0, graduatedTickUnit: 5,
          background: "transparent"
        },
        $(go.Shape, { geometryString: "M0 0 H400" }),
        $(go.Shape, { geometryString: "M0 0 V5" }),  // short tick mark
        $(go.Shape, { geometryString: "M0 0 V10", interval: 5 }),  // long tick mark
        $(go.TextBlock, { interval: 5, segmentOffset: new go.Point(0, 12) })
      ));

You can have more than one label. For example, small text that is more frequent than larger text:

    diagram.add(
      $(go.Part, "Graduated",
        {
          graduatedMin: 0, graduatedMax: 140,
          graduatedTickBase: 0, graduatedTickUnit: 5,
          background: "transparent"
        },
        $(go.Shape, { geometryString: "M0 0 H450" }),  // longer line
        $(go.Shape, { geometryString: "M0 0 V5" }),
        $(go.Shape, { geometryString: "M0 0 V10", interval: 4 }),
        // minor label
        $(go.TextBlock, { interval: 2, segmentOffset: new go.Point(0, 8),
                          stroke: "blue", font: "7pt sans-serif" }),
        // major label
        $(go.TextBlock, { interval: 4, segmentOffset: new go.Point(0, 12),
                          stroke: "red", font: "bold 12pt sans-serif" })
      ));

### Tick Mark Appearance

The appearance of tick marks relative to the main shape path is controlled by a few properties:

- Shape.graduatedStart/TextBlock.graduatedStart - the fractional distance along the main stroke at which drawing this tick or label may begin
- Shape.graduatedEnd/TextBlock.graduatedEnd - the fractional distance along the main stroke beyond which it will not draw this tick or label
- GraphObject.alignmentFocus - the spot on the tick or label to align with the calculated path points, defaulting to the top center
- GraphObject.segmentOffset - how much to offset a TextBlock label from the main stroke -- the Y value specifies distance from the path
- GraphObject.segmentOrientation - how to rotate a TextBlock label relative to the main stroke

Only TextBlock labels should set the GraphObject.segmentOffset or GraphObject.segmentOrientation. They have no impact on the main shape or tick shapes. These GraphObject properties are also commonly used to place Link labels, as seen in the Introduction page on Link labels, and are used by Graduated Panels in a similar manner.

Setting `graduatedStart` and/or `graduatedEnd` allows for drawing ticks only along part of the main stroke:

    diagram.add(
      $(go.Part, "Graduated",
        $(go.Shape, { geometryString: "M0 0 H400" }),
        $(go.Shape, { geometryString: "M0 0 V10", graduatedStart: .25, graduatedEnd: .75 })
      ));

In this case, tick marks are now only drawn in the middle half of the main shape.

Setting `alignmentFocus` to `go.Spot.Bottom` will cause the ticks to have their bottoms aligned to the main stroke:

    diagram.add(
      $(go.Part, "Graduated",
        $(go.Shape, { geometryString: "M0 0 H400" }),
        $(go.Shape, { geometryString: "M0 0 V10", alignmentFocus: go.Spot.Bottom })
      ));

Setting `alignmentFocus` to `go.Spot.Center` will cause the ticks to be centered across the path:

    diagram.add(
      $(go.Part, "Graduated",
        $(go.Shape, { geometryString: "M0 0 H400" }),
        $(go.Shape, { geometryString: "M0 0 V10 M0 20 V30", alignmentFocus: go.Spot.Center })
      ));

Note the gap in the geometry of the shape.

Setting `segmentOffset` for labels can make them more readable near tick marks:

    diagram.add(
      $(go.Part, "Graduated",
        $(go.Shape, { geometryString: "M0 0 H400" }),
        $(go.Shape, { geometryString: "M0 0 V10" }),
        // offset to display below ticks
        $(go.TextBlock, { segmentOffset: new go.Point(0, 12) })
      ));

Setting `segmentOrientation` for labels can alter the angle at which they are drawn relative to the main stroke:

    diagram.add(
      $(go.Part, "Graduated",
        $(go.Shape, { geometryString: "M0 0 H400" }),
        $(go.Shape, { geometryString: "M0 0 V10" }),
        // change the angle of the text
        $(go.TextBlock, { segmentOrientation: go.Link.OrientMinus90 })
      ));

Note that the top-center point of each label is exactly at the point along the path for that value.

Combining these two properties and re-aligning the tick marks:

    diagram.add(
      $(go.Part, "Graduated",
        $(go.Shape, { geometryString: "M0 0 H400" }),
        $(go.Shape, { geometryString: "M0 0 V10", alignmentFocus: go.Spot.Bottom }),
        $(go.TextBlock,
          {
            alignmentFocus: go.Spot.Left,
            segmentOffset: new go.Point(0, -12),
            segmentOrientation: go.Link.OrientMinus90
          }
        )
      ));

These properties behave similarly to Link labels, in that they respond to the direction of the main stroke. For example, let us turn the main shape so that it goes diagonally down from the top-left to the bottom-right.

    diagram.add(
      $(go.Part, "Graduated",
        $(go.Shape, { geometryString: "M0 0 L285 285" }),
        $(go.Shape, { geometryString: "M0 0 V10", alignmentFocus: go.Spot.Bottom }),
        $(go.TextBlock,
          {
            alignmentFocus: go.Spot.Left,
            segmentOffset: new go.Point(0, -12),
            segmentOrientation: go.Link.OrientMinus90
          }
        )
      ));

Now let us try a curve:

    diagram.add(
      $(go.Part, "Graduated",
        $(go.Shape, "Curve1", { desiredSize: new go.Size(285, 285) }),
        $(go.Shape, { geometryString: "M0 0 V10", alignmentFocus: go.Spot.Bottom }),
        $(go.TextBlock,
          {
            alignmentFocus: go.Spot.Left,
            segmentOffset: new go.Point(0, -12),
            segmentOrientation: go.Link.OrientMinus90
          }
        )
      ));

Here's another commonplace configuration:

    diagram.add(
      $(go.Part, "Graduated",
        $(go.Shape, { geometryString: "M0 0 A120 120 0 0 1 200 0" }),  // an arc
        $(go.Shape, { geometryString: "M0 0 V10" }),
        $(go.TextBlock,
          {
            segmentOffset: new go.Point(0, 12),
            segmentOrientation: go.Link.OrientAlong
          }
        )
      ));

For vertical lines, it's not necessary to rotate the text:

    diagram.add(
      $(go.Part, "Graduated",
        $(go.Shape, { geometryString: "M0 0 V400" }),
        $(go.Shape, { geometryString: "M0 0 V10", alignmentFocus: go.Spot.Bottom }),
        $(go.TextBlock,
          {
            alignmentFocus: go.Spot.Left,
            segmentOffset: new go.Point(0, -12)
          }
        )
      ));

We can also go from bottom to top:

    diagram.add(
      $(go.Part, "Graduated",
        $(go.Shape, { geometryString: "M0 0 V-400" }),
        $(go.Shape, { geometryString: "M0 0 V10", alignmentFocus: go.Spot.Top }),
        $(go.TextBlock,
          {
            alignmentFocus: go.Spot.Left,
            segmentOffset: new go.Point(0, 12)
          }
        )
      ));

Note how the Geometry goes from 0,0 to 0,-400, because negative Y values are higher on the screen/page. Note how because everything is relative to the path, the tick marks and labels would be on the opposite side, so we have also changed the `alignmentFocus` and `segmentOffset` to have opposite values from the previous example.

### Functional Appearance Properties

There are also some functional properties allowing for further customization of the appearance of ticks and labels.

- Shape.graduatedSkip/TextBlock.graduatedSkip - an optional function which returns true for values that should be skipped while drawing a particular tick or label
- TextBlock.graduatedFunction - an optional function which converts a value to a string to be displayed at that value -- if not defined, the default returns the value rounded to at most two decimals

Setting `graduatedSkip` allows for skipping ticks where the supplied function returns true:

      diagram.add(
        $(go.Part, "Graduated",
          $(go.Shape, { geometryString: "M0 0 H400" }),
          $(go.Shape,
            { // skip drawing tick at 30
              graduatedSkip: function (v) { return v === 30; },
              geometryString: "M0 0 V10"
            }
          ),
          $(go.TextBlock, { segmentOffset: new go.Point(0, 12) })
        ));

Setting `graduatedFunction` allows for changing the way labels are displayed:

      diagram.add(
        $(go.Part, "Graduated",
          $(go.Shape, { geometryString: "M0 0 H400" }),
          $(go.Shape, { geometryString: "M0 0 V10" }),
          $(go.TextBlock,
            { // always display two decimals
              graduatedFunction: function(val) { return val.toFixed(2); },
              segmentOffset: new go.Point(0, 12)
            }
          )
        ));

## Graduated Value Computations

There are some methods available for computing points along graduated paths:

- Panel.graduatedPointForValue - returns the Point along the main shape at some value between graduatedMin and graduatedMax in Panel coordinates
- Panel.graduatedValueForPoint - returns the value along the main shape nearest a given Point

In the following example, the red marker uses a Part.dragComputation function that keeps it along the path of the Graduated Panel using the above functions.

    var gauge =
      $(go.Part, "Auto",
        { location: new go.Point(10, 20) },
        $(go.Shape, { fill: "white" }),
        $(go.Panel, "Graduated",
          { name: "SCALE", margin: 10 },
          $(go.Shape, { name: "PATH", geometryString: "M0 0 A120 120 0 0 1 200 0" }),
          $(go.Shape, { geometryString: "M0 0 V10" }),
          $(go.TextBlock,
            { segmentOffset: new go.Point(0, 12), segmentOrientation: go.Link.OrientAlong })
        )
      );
    diagram.add(gauge);

    var marker =
      $(go.Part, "Spot",
        { locationSpot: go.Spot.Center, selectionAdorned: false },
        $(go.Shape, "Circle", { fill: "transparent", strokeWidth: 0, cursor: "pointer" }),
        $(go.Shape, "Circle", { fill: "red", strokeWidth: 0, width: 8, height: 8 }),
        {
          dragComputation: function(node, pt) {
            var scale = gauge.findObject("SCALE");
            var loc = scale.getLocalPoint(pt);
            var val = scale.graduatedValueForPoint(loc);
            var gpt = scale.graduatedPointForValue(val);
            return scale.getDocumentPoint(gpt);
          }
        }
      );
    diagram.add(marker);

    // once everything has been positioned, give the marker its location
    diagram.addDiagramListener("InitialLayoutCompleted", function(e) {
      var scale = gauge.findObject("SCALE");
      var gpt = scale.graduatedPointForValue(0);
      marker.location = scale.getDocumentPoint(gpt);
    });

As you drag the red circle, you will notice that it always stays on the main shape's stroke. The computation converts the point to the panel's coordinate system, computes the closest graduated value, computes the point on the shape geometry for that value, and finally converts it back to document coordinates for use as the marker's location.

Note that for demonstration purposes this example has the marker being a separate Part from the "gauge" Part. A real gauge would have the marker be part of the gauge as an indicator of a particular value.

## Other Considerations

By default, only the main shape of a Graduated Panel can be used to pick the panel. As with Grid Panels, a Graduated Panel should have a non-null `background` if the entire panel needs to be pickable. You cannot set or bind the Panel.itemArray of a Graduated Panel. You can set and bind properties on tick Shapes and TextBlock labels as you can with any other GraphObject properties.

    diagram.add(
      $(go.Part, "Graduated",  // or "Graduated"
        { background: "white" },
        $(go.Shape, { geometryString: "M0 0 H150", stroke: "blue", strokeWidth: 2 }),
        $(go.Shape, { geometryString: "M0 0 V20", stroke: "blue", strokeDashArray: [2, 2] })
      ));

Events on the tick Shapes and TextBlock labels will be ignored. Rotating the main shape will not rotate the ticks, just as rotating a Spot Panel's main element won't rotate its children. Rotation should generally be done at the Panel level. Another similarity to Spot Panels is that resizing of a Graduated Panel should generally be done on the main shape. TextBlock labels cannot be edited.