Text

Text mark displays each data item as text.

{
  "data": {
    "values": [
      { "x": 1, "text": "Hello" },
      { "x": 2, "text": "world!" }
    ]
  },
  "mark": "text",
  "encoding": {
    "x": { "field": "x", "type": "ordinal" },
    "color": { "field": "x", "type": "nominal" },
    "text": { "field": "text" },
    "size": { "value": 100 }
  }
}

Channels

In addition to primary and secondary position channels and color and opacity channels, point mark has the following channels:

text

Type: String

The text to display. The format of numeric data can be customized by setting a format specifier to channel definition's format property.

Default value: ""

size

Type: Number

The font size in pixels.

Default value: 11

angle

Type: Number

The rotation angle in degrees.

Default value: 0

Properties

font

Type: String

The font typeface. GenomeSpy uses SDF versions of Google Fonts. Check their availability at the A-Frame Fonts repository. The system fonts are not supported.

Default value: "Lato"

fontWeight

Type: String | Number

The font weight. The following strings and numbers are valid values: "thin" (100), "light" (300), "regular" (400), "normal" (400), "medium" (500), "bold" (700), "black" (900)

Default value: "regular"

fontStyle

Type: String

The font style. Valid values: "normal" and "italic".

Default value: "normal"

align

Type: String

The horizontal alignment of the text. One of "left", "center", or "right".

Default value: "left"

baseline

Type: String

The vertical alignment of the text. One of "top", "middle", "bottom".

Default value: "bottom"

dX

Type: Number

Offset of the x coordinate in pixels. The offset is applied after the viewport scaling and translation.

Default value: 0

dY

Type: Number

Offset of the x coordinate in pixels. The offset is applied after the viewport scaling and translation.

Default value: 0

fitToBand

Type: Boolean

If true, sets the secondary positional channel that allows the text to be squeezed (see the squeeze property). Can be used when: (1) "band", "index", or "locus" scale is being used and (2) only the primary positional channel is specified.

Default value: false

paddingX

Type: Number

The horizontal padding, in pixels, when the x2 channel is used for ranged text.

Default value: 0

paddingY

Type: Number

The vertical padding, in pixels, when the y2 channel is used for ranged text.

Default value: 0

flushX

Type: Boolean

If true, the text is kept inside the viewport when the range of x and x2 intersect the viewport.

Default value: true

flushY

Type: Boolean

If true, the text is kept inside the viewport when the range of y and y2 intersect the viewport.

Default value: true

squeeze

Type: Boolean

If the squeeze property is true and secondary positional channels (x2 and/or y2) are used, the text is scaled to fit mark's width and/or height.

Default value: true

logoLetters

Type: Boolean;

Stretch letters so that they can be used with sequence logos, etc...

Default value: false

Examples

GenomeSpy's text mark provides several tricks useful with segmented data and zoomable visualizations.

Ranged text

The x2 and y2 channels allow for positioning the text inside a segment. The text is either squeezed (default) or hidden when it does not fit in the segment. The squeeze property controls the behavior.

The example below has two layers: gray rectangles at the bottom and ranged text on the top. Try to zoom and pan to see how they behave!

{
  "data": {
    "values": ["A", "B", "C", "D", "E", "F", "G"]
  },
  "transform": [
    { "type": "formula", "expr": "round(random() * 100)", "as": "a" },
    { "type": "formula", "expr": "datum.a + round(random() * 60)", "as": "b" }
  ],
  "encoding": {
    "x": { "field": "a", "type": "quantitative", "scale": { "zoom": true } },
    "x2": { "field": "b" },
    "y": {
      "field": "data",
      "type": "nominal",
      "scale": {
        "padding": 0.3
      }
    }
  },
  "layer": [
    {
      "mark": "rect",
      "encoding": { "color": { "value": "#eaeaea" } }
    },
    {
      "mark": {
        "type": "text",
        "align": "center",
        "baseline": "middle",
        "paddingX": 5
      },
      "encoding": {
        "text": {
          "expr": "'Hello ' + floor(datum.a)"
        },
        "size": { "value": 12 }
      }
    }
  ]
}

Sequence logo

The example below demonstrates the use of the logoLetters, squeeze, and fitToBand properties to ensure that the letters fully cover the rectangles defined by the primary and secondary positional channels. Not all fonts look good in sequence logos, but Source Sans Pro seems decent.

{
  "data": {
    "values": [
      { "pos": 1, "base": "A", "count": 2 },
      { "pos": 1, "base": "C", "count": 3 },
      { "pos": 1, "base": "T", "count": 5 },
      { "pos": 2, "base": "A", "count": 7 },
      { "pos": 2, "base": "C", "count": 3 },
      { "pos": 3, "base": "A", "count": 10 },
      { "pos": 4, "base": "T", "count": 9 },
      { "pos": 4, "base": "G", "count": 1 },
      { "pos": 5, "base": "G", "count": 8 },
      { "pos": 6, "base": "G", "count": 7 }
    ]
  },
  "transform": [
    {
      "type": "stack",
      "field": "count",
      "groupby": ["pos"],
      "offset": "information",
      "as": ["_y0", "_y1"],
      "baseField": "base",
      "sort": { "field": "count", "order": "ascending" }
    }
  ],
  "encoding": {
    "x": { "field": "pos", "type": "index" },
    "y": {
      "field": "_y0",
      "type": "quantitative",
      "scale": { "domain": [0, 2] },
      "title": "Information"
    },
    "y2": { "field": "_y1" },
    "text": { "field": "base", "type": "nominal" },
    "color": {
      "field": "base",
      "type": "nominal",
      "scale": {
        "type": "ordinal",
        "domain": ["A", "C", "T", "G"],
        "range": ["#7BD56C", "#FF9B9B", "#86BBF1", "#FFC56C"]
      }
    }
  },
  "mark": {
    "type": "text",
    "font": "Source Sans Pro",
    "fontWeight": 700,
    "size": 100,
    "squeeze": true,
    "fitToBand": true,

    "paddingX": 0,
    "paddingY": 0,

    "logoLetters": true
  }
}