interactive_brush.vg.json

{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "description": "Drag out a rectangular brush to highlight points.",
  "background": "white",
  "padding": 5,
  "width": 200,
  "height": 200,
  "style": "cell",
  "data": [
    {
      "name": "brush_store",
      "values": [
        {
          "unit": "",
          "fields": [
            {"field": "Horsepower", "channel": "x", "type": "R", "index": 0},
            {
              "field": "Miles_per_Gallon",
              "channel": "y",
              "type": "R",
              "index": 1
            }
          ],
          "values": [[55, 160], [13, 37]]
        }
      ]
    },
    {
      "name": "source_0",
      "url": "data/cars.json",
      "format": {"type": "json"},
      "transform": [
        {
          "type": "filter",
          "expr": "isValid(datum[\"Horsepower\"]) && isFinite(+datum[\"Horsepower\"]) && isValid(datum[\"Miles_per_Gallon\"]) && isFinite(+datum[\"Miles_per_Gallon\"])"
        }
      ]
    }
  ],
  "signals": [
    {
      "name": "unit",
      "value": {},
      "on": [
        {"events": "mousemove", "update": "isTuple(group()) ? group() : unit"}
      ]
    },
    {
      "name": "brush",
      "update": "vlSelectionResolve(\"brush_store\", \"union\")"
    },
    {
      "name": "brush_x",
      "init": "[scale(\"x\", 55), scale(\"x\", 160)]",
      "on": [
        {
          "events": {
            "source": "scope",
            "type": "mousedown",
            "filter": [
              "!event.item || event.item.mark.name !== \"brush_brush\""
            ]
          },
          "update": "[x(unit), x(unit)]"
        },
        {
          "events": {
            "source": "window",
            "type": "mousemove",
            "consume": true,
            "between": [
              {
                "source": "scope",
                "type": "mousedown",
                "filter": [
                  "!event.item || event.item.mark.name !== \"brush_brush\""
                ]
              },
              {"source": "window", "type": "mouseup"}
            ]
          },
          "update": "[brush_x[0], clamp(x(unit), 0, width)]"
        },
        {
          "events": {"signal": "brush_scale_trigger"},
          "update": "[scale(\"x\", brush_Horsepower[0]), scale(\"x\", brush_Horsepower[1])]"
        },
        {
          "events": [{"source": "view", "type": "dblclick"}],
          "update": "[0, 0]"
        },
        {
          "events": {"signal": "brush_translate_delta"},
          "update": "clampRange(panLinear(brush_translate_anchor.extent_x, brush_translate_delta.x / span(brush_translate_anchor.extent_x)), 0, width)"
        },
        {
          "events": {"signal": "brush_zoom_delta"},
          "update": "clampRange(zoomLinear(brush_x, brush_zoom_anchor.x, brush_zoom_delta), 0, width)"
        }
      ]
    },
    {
      "name": "brush_Horsepower",
      "init": "[55, 160]",
      "on": [
        {
          "events": {"signal": "brush_x"},
          "update": "brush_x[0] === brush_x[1] ? null : invert(\"x\", brush_x)"
        }
      ]
    },
    {
      "name": "brush_y",
      "init": "[scale(\"y\", 13), scale(\"y\", 37)]",
      "on": [
        {
          "events": {
            "source": "scope",
            "type": "mousedown",
            "filter": [
              "!event.item || event.item.mark.name !== \"brush_brush\""
            ]
          },
          "update": "[y(unit), y(unit)]"
        },
        {
          "events": {
            "source": "window",
            "type": "mousemove",
            "consume": true,
            "between": [
              {
                "source": "scope",
                "type": "mousedown",
                "filter": [
                  "!event.item || event.item.mark.name !== \"brush_brush\""
                ]
              },
              {"source": "window", "type": "mouseup"}
            ]
          },
          "update": "[brush_y[0], clamp(y(unit), 0, height)]"
        },
        {
          "events": {"signal": "brush_scale_trigger"},
          "update": "[scale(\"y\", brush_Miles_per_Gallon[0]), scale(\"y\", brush_Miles_per_Gallon[1])]"
        },
        {
          "events": [{"source": "view", "type": "dblclick"}],
          "update": "[0, 0]"
        },
        {
          "events": {"signal": "brush_translate_delta"},
          "update": "clampRange(panLinear(brush_translate_anchor.extent_y, brush_translate_delta.y / span(brush_translate_anchor.extent_y)), 0, height)"
        },
        {
          "events": {"signal": "brush_zoom_delta"},
          "update": "clampRange(zoomLinear(brush_y, brush_zoom_anchor.y, brush_zoom_delta), 0, height)"
        }
      ]
    },
    {
      "name": "brush_Miles_per_Gallon",
      "init": "[13, 37]",
      "on": [
        {
          "events": {"signal": "brush_y"},
          "update": "brush_y[0] === brush_y[1] ? null : invert(\"y\", brush_y)"
        }
      ]
    },
    {
      "name": "brush_scale_trigger",
      "value": {},
      "on": [
        {
          "events": [{"scale": "x"}, {"scale": "y"}],
          "update": "(!isArray(brush_Horsepower) || (+invert(\"x\", brush_x)[0] === +brush_Horsepower[0] && +invert(\"x\", brush_x)[1] === +brush_Horsepower[1])) && (!isArray(brush_Miles_per_Gallon) || (+invert(\"y\", brush_y)[0] === +brush_Miles_per_Gallon[0] && +invert(\"y\", brush_y)[1] === +brush_Miles_per_Gallon[1])) ? brush_scale_trigger : {}"
        }
      ]
    },
    {
      "name": "brush_tuple",
      "init": "{unit: \"\", fields: brush_tuple_fields, values: [[55, 160], [13, 37]]}",
      "on": [
        {
          "events": [{"signal": "brush_Horsepower || brush_Miles_per_Gallon"}],
          "update": "brush_Horsepower && brush_Miles_per_Gallon ? {unit: \"\", fields: brush_tuple_fields, values: [brush_Horsepower,brush_Miles_per_Gallon]} : null"
        }
      ]
    },
    {
      "name": "brush_tuple_fields",
      "value": [
        {"field": "Horsepower", "channel": "x", "type": "R", "index": 0},
        {"field": "Miles_per_Gallon", "channel": "y", "type": "R", "index": 1}
      ]
    },
    {
      "name": "brush_translate_anchor",
      "value": {},
      "on": [
        {
          "events": [
            {"source": "scope", "type": "mousedown", "markname": "brush_brush"}
          ],
          "update": "{x: x(unit), y: y(unit), extent_x: slice(brush_x), extent_y: slice(brush_y)}"
        }
      ]
    },
    {
      "name": "brush_translate_delta",
      "value": {},
      "on": [
        {
          "events": [
            {
              "source": "window",
              "type": "mousemove",
              "consume": true,
              "between": [
                {
                  "source": "scope",
                  "type": "mousedown",
                  "markname": "brush_brush"
                },
                {"source": "window", "type": "mouseup"}
              ]
            }
          ],
          "update": "{x: brush_translate_anchor.x - x(unit), y: brush_translate_anchor.y - y(unit)}"
        }
      ]
    },
    {
      "name": "brush_zoom_anchor",
      "on": [
        {
          "events": [
            {
              "source": "scope",
              "type": "wheel",
              "consume": true,
              "markname": "brush_brush"
            }
          ],
          "update": "{x: x(unit), y: y(unit)}"
        }
      ]
    },
    {
      "name": "brush_zoom_delta",
      "on": [
        {
          "events": [
            {
              "source": "scope",
              "type": "wheel",
              "consume": true,
              "markname": "brush_brush"
            }
          ],
          "force": true,
          "update": "pow(1.001, event.deltaY * pow(16, event.deltaMode))"
        }
      ]
    },
    {
      "name": "brush_modify",
      "on": [
        {
          "events": {"signal": "brush_tuple"},
          "update": "modify(\"brush_store\", brush_tuple, true)"
        }
      ]
    }
  ],
  "marks": [
    {
      "name": "brush_brush_bg",
      "type": "rect",
      "clip": true,
      "encode": {
        "enter": {"fill": {"value": "#333"}, "fillOpacity": {"value": 0.125}},
        "update": {
          "x": [
            {
              "test": "data(\"brush_store\").length && data(\"brush_store\")[0].unit === \"\"",
              "signal": "brush_x[0]"
            },
            {"value": 0}
          ],
          "y": [
            {
              "test": "data(\"brush_store\").length && data(\"brush_store\")[0].unit === \"\"",
              "signal": "brush_y[0]"
            },
            {"value": 0}
          ],
          "x2": [
            {
              "test": "data(\"brush_store\").length && data(\"brush_store\")[0].unit === \"\"",
              "signal": "brush_x[1]"
            },
            {"value": 0}
          ],
          "y2": [
            {
              "test": "data(\"brush_store\").length && data(\"brush_store\")[0].unit === \"\"",
              "signal": "brush_y[1]"
            },
            {"value": 0}
          ]
        }
      }
    },
    {
      "name": "marks",
      "type": "symbol",
      "style": ["point"],
      "interactive": true,
      "from": {"data": "source_0"},
      "encode": {
        "update": {
          "opacity": {"value": 0.7},
          "fill": {"value": "transparent"},
          "stroke": [
            {
              "test": "!length(data(\"brush_store\")) || vlSelectionTest(\"brush_store\", datum)",
              "scale": "color",
              "field": "Cylinders"
            },
            {"value": "grey"}
          ],
          "ariaRoleDescription": {"value": "point"},
          "description": {
            "signal": "\"Horsepower: \" + (format(datum[\"Horsepower\"], \"\")) + \"; Miles_per_Gallon: \" + (format(datum[\"Miles_per_Gallon\"], \"\")) + \"; Cylinders: \" + (isValid(datum[\"Cylinders\"]) ? datum[\"Cylinders\"] : \"\"+datum[\"Cylinders\"])"
          },
          "x": {"scale": "x", "field": "Horsepower"},
          "y": {"scale": "y", "field": "Miles_per_Gallon"}
        }
      }
    },
    {
      "name": "brush_brush",
      "type": "rect",
      "clip": true,
      "encode": {
        "enter": {"fill": {"value": "transparent"}},
        "update": {
          "x": [
            {
              "test": "data(\"brush_store\").length && data(\"brush_store\")[0].unit === \"\"",
              "signal": "brush_x[0]"
            },
            {"value": 0}
          ],
          "y": [
            {
              "test": "data(\"brush_store\").length && data(\"brush_store\")[0].unit === \"\"",
              "signal": "brush_y[0]"
            },
            {"value": 0}
          ],
          "x2": [
            {
              "test": "data(\"brush_store\").length && data(\"brush_store\")[0].unit === \"\"",
              "signal": "brush_x[1]"
            },
            {"value": 0}
          ],
          "y2": [
            {
              "test": "data(\"brush_store\").length && data(\"brush_store\")[0].unit === \"\"",
              "signal": "brush_y[1]"
            },
            {"value": 0}
          ],
          "stroke": [
            {
              "test": "brush_x[0] !== brush_x[1] && brush_y[0] !== brush_y[1]",
              "value": "white"
            },
            {"value": null}
          ]
        }
      }
    }
  ],
  "scales": [
    {
      "name": "x",
      "type": "linear",
      "domain": {"data": "source_0", "field": "Horsepower"},
      "range": [0, {"signal": "width"}],
      "nice": true,
      "zero": true
    },
    {
      "name": "y",
      "type": "linear",
      "domain": {"data": "source_0", "field": "Miles_per_Gallon"},
      "range": [{"signal": "height"}, 0],
      "nice": true,
      "zero": true
    },
    {
      "name": "color",
      "type": "ordinal",
      "domain": {"data": "source_0", "field": "Cylinders", "sort": true},
      "range": "ordinal",
      "interpolate": "hcl"
    }
  ],
  "axes": [
    {
      "scale": "x",
      "orient": "bottom",
      "gridScale": "y",
      "grid": true,
      "tickCount": {"signal": "ceil(width/40)"},
      "domain": false,
      "labels": false,
      "aria": false,
      "maxExtent": 0,
      "minExtent": 0,
      "ticks": false,
      "zindex": 0
    },
    {
      "scale": "y",
      "orient": "left",
      "gridScale": "x",
      "grid": true,
      "tickCount": {"signal": "ceil(height/40)"},
      "domain": false,
      "labels": false,
      "aria": false,
      "maxExtent": 0,
      "minExtent": 0,
      "ticks": false,
      "zindex": 0
    },
    {
      "scale": "x",
      "orient": "bottom",
      "grid": false,
      "title": "Horsepower",
      "labelFlush": true,
      "labelOverlap": true,
      "tickCount": {"signal": "ceil(width/40)"},
      "zindex": 0
    },
    {
      "scale": "y",
      "orient": "left",
      "grid": false,
      "title": "Miles_per_Gallon",
      "labelOverlap": true,
      "tickCount": {"signal": "ceil(height/40)"},
      "zindex": 0
    }
  ],
  "legends": [
    {
      "stroke": "color",
      "symbolType": "circle",
      "title": "Cylinders",
      "encode": {
        "symbols": {
          "update": {
            "fill": {"value": "transparent"},
            "opacity": {"value": 0.7}
          }
        }
      }
    }
  ]
}