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Heatmapgl

Overview

The heatmapgl trace type is similar to the regular heatmap but is rendered using WebGL for faster and more performant rendering of large datasets. This trace type is ideal for heatmaps with many data points, as it leverages GPU acceleration.

You can customize the colorscale, text annotations, and other properties to create high-performance heatmaps for large-scale data.

Common Uses

  • High-Performance Heatmaps: Visualizing large datasets efficiently.
  • Big Data Visualization: Rendering heatmaps with thousands or millions of points.
  • Correlation Matrices & Density Maps: Displaying data where relationships or density are critical to analyze.

Check out the Attributes for the full set of configuration options

Examples

Common Configurations

Here's a simple heatmapgl plot, showing a grid of data values efficiently rendered using WebGL:

You can copy this code below to create this chart in your project:

models:
  - name: heatmapgl-data
    args:
      - echo
      - |
        x,y,z
        A,1,10
        A,2,20
        A,3,30
        B,1,40
        B,2,50
        B,3,60
        C,1,70
        C,2,80
        C,3,90
traces:
  - name: Simple Heatmapgl Plot
    model: ref(heatmapgl-data)
    props:
      type: heatmapgl
      x: query(x)
      y: query(y)
      z: query(z)
      colorscale: "Viridis"
charts:
  - name: Simple Heatmapgl Chart
    traces:
      - ref(Simple Heatmapgl Plot)
    layout:
      title:
        text: Simple Heatmapgl Plot<br><sub>Efficient Heatmap Rendering with WebGL</sub>
      xaxis:
        title:
          text: "X Axis"
      yaxis:
        title:
          text: "Y Axis"

This example shows a heatmapgl plot with a custom colorscale, providing fine-grained control over the color mapping:

Here's the code:

models:
  - name: heatmapgl-data-custom
    args:
      - echo
      - |
        x,y,z
        1,1,0.5
        1,2,0.6
        1,3,0.7
        2,1,0.8
        2,2,0.9
        2,3,1.0
        3,1,0.1
        3,2,0.2
        3,3,0.3
traces:
  - name: Heatmapgl with Custom Colorscale
    model: ref(heatmapgl-data-custom)
    props:
      type: heatmapgl
      x: query(x)
      y: query(y)
      z: query(z)
      colorscale: [[0, "rgb(255,245,240)"], [0.5, "rgb(252,146,114)"], [1, "rgb(165,15,21)"]]
      zmin: 0
      zmax: 1
charts:
  - name: Heatmapgl Chart with Custom Colorscale
    traces:
      - ref(Heatmapgl with Custom Colorscale)
    layout:
      title:
        text: Heatmapgl with Custom Colorscale<br><sub>Custom Coloring for Large Data</sub>
      xaxis:
        title:
          text: "X Axis"
      yaxis:
        title:
          text: "Y Axis"

Here's a heatmapgl plot that demonstrates how WebGL allows efficient rendering of large datasets. This example simulates a larger data set with many points:

Here's the code:

models:
  - name: heatmapgl-data-large
    args:
      - echo
      - |
        x,y,z
        1,1,1
        1,2,2
        1,3,3
        1,4,4
        1,5,5
        2,1,6
        2,2,7
        2,3,8
        2,4,9
        2,5,10
        3,1,11
        3,2,12
        3,3,13
        3,4,14
        3,5,15
traces:
  - name: Heatmapgl for Large Datasets
    model: ref(heatmapgl-data-large)
    props:
      type: heatmapgl
      x: query(x)
      y: query(y)
      z: query(z)
      colorscale: "Jet"
      zmin: 0
      zmax: 15
charts:
  - name: Heatmapgl Chart for Large Datasets
    traces:
      - ref(Heatmapgl for Large Datasets)
    layout:
      title:
        text: Heatmapgl for Large Datasets<br><sub>WebGL Rendered Heatmap for Large Data</sub>
      xaxis:
        title:
          text: "X Axis"
      yaxis:
        title:
          text: "Y Axis"

Attributes

These attributes apply to traces where trace.props.type is set to heatmapgl. You would configure these attributes on the trace with the trace.props object. 

autocolorscale: 'boolean' #(1)!
coloraxis: 'subplotid' #(2)!
colorbar:
  bgcolor: 'color' #(3)!
  bordercolor: 'color' #(4)!
  borderwidth: 'number greater than or equal to 0' #(5)!
  dtick: 'number or categorical coordinate string' #(6)!
  exponentformat: 'enumerated , one of ( "none" | "e" | "e" | "power" | "si" | "b"
    )' #(7)!
  len: 'number greater than or equal to 0' #(8)!
  lenmode: 'enumerated , one of ( "fraction" | "pixels" )' #(9)!
  minexponent: 'number greater than or equal to 0' #(10)!
  nticks: 'integer greater than or equal to 0' #(11)!
  orientation: 'enumerated , one of ( "h" | "v" )' #(12)!
  outlinecolor: 'color' #(13)!
  outlinewidth: 'number greater than or equal to 0' #(14)!
  separatethousands: 'boolean' #(15)!
  showexponent: 'enumerated , one of ( "all" | "first" | "last" | "none" )' #(16)!
  showticklabels: 'boolean' #(17)!
  showtickprefix: 'enumerated , one of ( "all" | "first" | "last" | "none" )' #(18)!
  showticksuffix: 'enumerated , one of ( "all" | "first" | "last" | "none" )' #(19)!
  thickness: 'number greater than or equal to 0' #(20)!
  thicknessmode: 'enumerated , one of ( "fraction" | "pixels" )' #(21)!
  tick0: 'number or categorical coordinate string' #(22)!
  tickangle: 'angle' #(23)!
  tickcolor: 'color' #(24)!
  tickfont:
    color: color
    family: 'string' #(25)!
    size: number greater than or equal to 1
  tickformat: 'string' #(26)!
  tickformatstops:
    dtickrange: 'array' #(27)!
    enabled: 'boolean' #(28)!
    name: 'string' #(29)!
    templateitemname: 'string' #(30)!
    value: 'string' #(31)!
  ticklabeloverflow: 'enumerated , one of ( "allow" | "hide past div" | "hide past
    domain" )' #(32)!
  ticklabelposition: 'enumerated , one of ( "outside" | "inside" | "outside top" |
    "inside top" | "outside left" | "inside left" | "outside right" | "inside right"
    | "outside bottom" | "inside bottom" )' #(33)!
  ticklabelstep: 'integer greater than or equal to 1' #(34)!
  ticklen: 'number greater than or equal to 0' #(35)!
  tickmode: 'enumerated , one of ( "auto" | "linear" | "array" )' #(36)!
  tickprefix: 'string' #(37)!
  ticks: 'enumerated , one of ( "outside" | "inside" | "" )' #(38)!
  ticksuffix: 'string' #(39)!
  ticktext: 'data array' #(40)!
  tickvals: 'data array' #(41)!
  tickwidth: 'number greater than or equal to 0' #(42)!
  title:
    font:
      color: color
      family: 'string' #(43)!
      size: number greater than or equal to 1
    side: 'enumerated , one of ( "right" | "top" | "bottom" )' #(44)!
    text: 'string' #(45)!
  x: 'number between or equal to -2 and 3' #(46)!
  xanchor: 'enumerated , one of ( "left" | "center" | "right" )' #(47)!
  xpad: 'number greater than or equal to 0' #(48)!
  y: 'number between or equal to -2 and 3' #(49)!
  yanchor: 'enumerated , one of ( "top" | "middle" | "bottom" )' #(50)!
  ypad: 'number greater than or equal to 0' #(51)!
colorscale: 'colorscale' #(52)!
customdata: 'data array' #(53)!
dx: 'number' #(54)!
dy: 'number' #(55)!
hoverinfo: 'flaglist string. any combination of "x", "y", "z", "text", "name" joined
  with a "+" or "all" or "none" or "skip".' #(56)!
hoverlabel:
  align: 'enumerated or array of enumerateds , one of ( "left" | "right" | "auto"
    )' #(57)!
  bgcolor: 'color or array of colors' #(58)!
  bordercolor: 'color or array of colors' #(59)!
  font:
    color: color or array of colors
    family: 'string or array of strings' #(60)!
    size: number or array of numbers greater than or equal to 1
  namelength: 'integer or array of integers greater than or equal to -1' #(61)!
ids: 'data array' #(62)!
legendgrouptitle:
  font:
    color: color
    family: 'string' #(63)!
    size: number greater than or equal to 1
  text: 'string' #(64)!
legendrank: 'number' #(65)!
legendwidth: 'number greater than or equal to 0' #(66)!
meta: 'number or categorical coordinate string' #(67)!
opacity: 'number between or equal to 0 and 1' #(68)!
reversescale: 'boolean' #(69)!
showscale: 'boolean' #(70)!
text: 'data array' #(71)!
transpose: 'boolean' #(72)!
type: heatmapgl
uirevision: 'number or categorical coordinate string' #(73)!
visible: 'enumerated , one of ( true | false | "legendonly" )' #(74)!
x: 'data array' #(76)!
x0: 'number or categorical coordinate string' #(75)!
xaxis: 'subplotid' #(77)!
xtype: 'enumerated , one of ( "array" | "scaled" )' #(78)!
y: 'data array' #(80)!
y0: 'number or categorical coordinate string' #(79)!
yaxis: 'subplotid' #(81)!
ytype: 'enumerated , one of ( "array" | "scaled" )' #(82)!
z: 'data array' #(83)!
zauto: 'boolean' #(84)!
zmax: 'number' #(85)!
zmid: 'number' #(86)!
zmin: 'number' #(87)!
zsmooth: 'enumerated , one of ( "fast" | false )' #(88)!
  1. Determines whether the colorscale is a default palette (autocolorscale: true) or the palette determined by colorscale. In case colorscale is unspecified or autocolorscale is true, the default palette will be chosen according to whether numbers in the color array are all positive, all negative or mixed.
  2. Sets a reference to a shared color axis. References to these shared color axes are "coloraxis", "coloraxis2", "coloraxis3", etc. Settings for these shared color axes are set in the layout, under layout.coloraxis, layout.coloraxis2, etc. Note that multiple color scales can be linked to the same color axis.
  3. Sets the color of padded area.
  4. Sets the axis line color.
  5. Sets the width (in px) or the border enclosing this color bar.
  6. Sets the step in-between ticks on this axis. Use with tick0. Must be a positive number, or special strings available to "log" and "date" axes. If the axis type is "log", then ticks are set every 10^(n"dtick) where n is the tick number. For example, to set a tick mark at 1, 10, 100, 1000, ... set dtick to 1. To set tick marks at 1, 100, 10000, ... set dtick to 2. To set tick marks at 1, 5, 25, 125, 625, 3125, ... set dtick to log_10(5), or 0.69897000433. "log" has several special values; "L", where f is a positive number, gives ticks linearly spaced in value (but not position). For example tick0 = 0.1, dtick = "L0.5" will put ticks at 0.1, 0.6, 1.1, 1.6 etc. To show powers of 10 plus small digits between, use "D1" (all digits) or "D2" (only 2 and 5). tick0 is ignored for "D1" and "D2". If the axis type is "date", then you must convert the time to milliseconds. For example, to set the interval between ticks to one day, set dtick to 86400000.0. "date" also has special values "M" gives ticks spaced by a number of months. n must be a positive integer. To set ticks on the 15th of every third month, set tick0 to "2000-01-15" and dtick to "M3". To set ticks every 4 years, set dtick to "M48"
  7. Determines a formatting rule for the tick exponents. For example, consider the number 1,000,000,000. If "none", it appears as 1,000,000,000. If "e", 1e+9. If "E", 1E+9. If "power", 1x10^9 (with 9 in a super script). If "SI", 1G. If "B", 1B.
  8. Sets the length of the color bar This measure excludes the padding of both ends. That is, the color bar length is this length minus the padding on both ends.
  9. Determines whether this color bar's length (i.e. the measure in the color variation direction) is set in units of plot "fraction" or in "pixels. Use len to set the value.
  10. Hide SI prefix for 10^n if |n| is below this number. This only has an effect when tickformat is "SI" or "B".
  11. Specifies the maximum number of ticks for the particular axis. The actual number of ticks will be chosen automatically to be less than or equal to nticks. Has an effect only if tickmode is set to "auto".
  12. Sets the orientation of the colorbar.
  13. Sets the axis line color.
  14. Sets the width (in px) of the axis line.
  15. If "true", even 4-digit integers are separated
  16. If "all", all exponents are shown besides their significands. If "first", only the exponent of the first tick is shown. If "last", only the exponent of the last tick is shown. If "none", no exponents appear.
  17. Determines whether or not the tick labels are drawn.
  18. If "all", all tick labels are displayed with a prefix. If "first", only the first tick is displayed with a prefix. If "last", only the last tick is displayed with a suffix. If "none", tick prefixes are hidden.
  19. Same as showtickprefix but for tick suffixes.
  20. Sets the thickness of the color bar This measure excludes the size of the padding, ticks and labels.
  21. Determines whether this color bar's thickness (i.e. the measure in the constant color direction) is set in units of plot "fraction" or in "pixels". Use thickness to set the value.
  22. Sets the placement of the first tick on this axis. Use with dtick. If the axis type is "log", then you must take the log of your starting tick (e.g. to set the starting tick to 100, set the tick0 to 2) except when dtick="L" (see dtick for more info). If the axis type is "date", it should be a date string, like date data. If the axis type is "category", it should be a number, using the scale where each category is assigned a serial number from zero in the order it appears.
  23. Sets the angle of the tick labels with respect to the horizontal. For example, a tickangle of -90 draws the tick labels vertically.
  24. Sets the tick color.
  25. HTML font family - the typeface that will be applied by the web browser. The web browser will only be able to apply a font if it is available on the system which it operates. Provide multiple font families, separated by commas, to indicate the preference in which to apply fonts if they aren't available on the system. The Chart Studio Cloud (at https://chart-studio.plotly.com or on-premise) generates images on a server, where only a select number of fonts are installed and supported. These include "Arial", "Balto", "Courier New", "Droid Sans",, "Droid Serif", "Droid Sans Mono", "Gravitas One", "Old Standard TT", "Open Sans", "Overpass", "PT Sans Narrow", "Raleway", "Times New Roman".
  26. Sets the tick label formatting rule using d3 formatting mini-languages which are very similar to those in Python. For numbers, see: https://github.com/d3/d3-format/tree/v1.4.5#d3-format. And for dates see: https://github.com/d3/d3-time-format/tree/v2.2.3#locale_format. We add two items to d3's date formatter: "%h" for half of the year as a decimal number as well as "%{n}f" for fractional seconds with n digits. For example, "2016-10-13 09:15:23.456" with tickformat "%H~%M~%S.%2f" would display "09~15~23.46"
  27. range ["min", "max"], where "min", "max" - dtick values which describe some zoom level, it is possible to omit "min" or "max" value by passing "null"
  28. Determines whether or not this stop is used. If false, this stop is ignored even within its dtickrange.
  29. When used in a template, named items are created in the output figure in addition to any items the figure already has in this array. You can modify these items in the output figure by making your own item with templateitemname matching this name alongside your modifications (including visible: false or enabled: false to hide it). Has no effect outside of a template.
  30. Used to refer to a named item in this array in the template. Named items from the template will be created even without a matching item in the input figure, but you can modify one by making an item with templateitemname matching its name, alongside your modifications (including visible: false or enabled: false to hide it). If there is no template or no matching item, this item will be hidden unless you explicitly show it with visible: true.
  31. string - dtickformat for described zoom level, the same as "tickformat"
  32. Determines how we handle tick labels that would overflow either the graph div or the domain of the axis. The default value for inside tick labels is "hide past domain". In other cases the default is "hide past div".
  33. Determines where tick labels are drawn relative to the ticks. Left and right options are used when orientation is "h", top and bottom when orientation is "v".
  34. Sets the spacing between tick labels as compared to the spacing between ticks. A value of 1 (default) means each tick gets a label. A value of 2 means shows every 2nd label. A larger value n means only every nth tick is labeled. tick0 determines which labels are shown. Not implemented for axes with type "log" or "multicategory", or when tickmode is "array".
  35. Sets the tick length (in px).
  36. Sets the tick mode for this axis. If "auto", the number of ticks is set via nticks. If "linear", the placement of the ticks is determined by a starting position tick0 and a tick step dtick ("linear" is the default value if tick0 and dtick are provided). If "array", the placement of the ticks is set via tickvals and the tick text is ticktext. ("array" is the default value if tickvals is provided).
  37. Sets a tick label prefix.
  38. Determines whether ticks are drawn or not. If "", this axis' ticks are not drawn. If "outside" ("inside"), this axis' are drawn outside (inside) the axis lines.
  39. Sets a tick label suffix.
  40. Sets the text displayed at the ticks position via tickvals. Only has an effect if tickmode is set to "array". Used with tickvals.
  41. Sets the values at which ticks on this axis appear. Only has an effect if tickmode is set to "array". Used with ticktext.
  42. Sets the tick width (in px).
  43. HTML font family - the typeface that will be applied by the web browser. The web browser will only be able to apply a font if it is available on the system which it operates. Provide multiple font families, separated by commas, to indicate the preference in which to apply fonts if they aren't available on the system. The Chart Studio Cloud (at https://chart-studio.plotly.com or on-premise) generates images on a server, where only a select number of fonts are installed and supported. These include "Arial", "Balto", "Courier New", "Droid Sans",, "Droid Serif", "Droid Sans Mono", "Gravitas One", "Old Standard TT", "Open Sans", "Overpass", "PT Sans Narrow", "Raleway", "Times New Roman".
  44. Determines the location of color bar's title with respect to the color bar. Defaults to "top" when orientation if "v" and defaults to "right" when orientation if "h". Note that the title's location used to be set by the now deprecated titleside attribute.
  45. Sets the title of the color bar. Note that before the existence of title.text, the title's contents used to be defined as the title attribute itself. This behavior has been deprecated.
  46. Sets the x position of the color bar (in plot fraction). Defaults to 1.02 when orientation is "v" and 0.5 when orientation is "h".
  47. Sets this color bar's horizontal position anchor. This anchor binds the x position to the "left", "center" or "right" of the color bar. Defaults to "left" when orientation is "v" and "center" when orientation is "h".
  48. Sets the amount of padding (in px) along the x direction.
  49. Sets the y position of the color bar (in plot fraction). Defaults to 0.5 when orientation is "v" and 1.02 when orientation is "h".
  50. Sets this color bar's vertical position anchor This anchor binds the y position to the "top", "middle" or "bottom" of the color bar. Defaults to "middle" when orientation is "v" and "bottom" when orientation is "h".
  51. Sets the amount of padding (in px) along the y direction.
  52. Sets the colorscale. The colorscale must be an array containing arrays mapping a normalized value to an rgb, rgba, hex, hsl, hsv, or named color string. At minimum, a mapping for the lowest (0) and highest (1) values are required. For example, [[0, 'rgb(0,0,255)'], [1, 'rgb(255,0,0)']]. To control the bounds of the colorscale in color space, use zmin and zmax. Alternatively, colorscale may be a palette name string of the following list: Blackbody,Bluered,Blues,Cividis,Earth,Electric,Greens,Greys,Hot,Jet,Picnic,Portland,Rainbow,RdBu,Reds,Viridis,YlGnBu,YlOrRd.
  53. Assigns extra data each datum. This may be useful when listening to hover, click and selection events. Note that, "scatter" traces also appends customdata items in the markers DOM elements
  54. Sets the x coordinate step. See x0 for more info.
  55. Sets the y coordinate step. See y0 for more info.
  56. Determines which trace information appear on hover. If none or skip are set, no information is displayed upon hovering. But, if none is set, click and hover events are still fired.
  57. Sets the horizontal alignment of the text content within hover label box. Has an effect only if the hover label text spans more two or more lines
  58. Sets the background color of the hover labels for this trace
  59. Sets the border color of the hover labels for this trace.
  60. HTML font family - the typeface that will be applied by the web browser. The web browser will only be able to apply a font if it is available on the system which it operates. Provide multiple font families, separated by commas, to indicate the preference in which to apply fonts if they aren't available on the system. The Chart Studio Cloud (at https://chart-studio.plotly.com or on-premise) generates images on a server, where only a select number of fonts are installed and supported. These include "Arial", "Balto", "Courier New", "Droid Sans",, "Droid Serif", "Droid Sans Mono", "Gravitas One", "Old Standard TT", "Open Sans", "Overpass", "PT Sans Narrow", "Raleway", "Times New Roman".
  61. Sets the default length (in number of characters) of the trace name in the hover labels for all traces. -1 shows the whole name regardless of length. 0-3 shows the first 0-3 characters, and an integer >3 will show the whole name if it is less than that many characters, but if it is longer, will truncate to namelength - 3 characters and add an ellipsis.
  62. Assigns id labels to each datum. These ids for object constancy of data points during animation. Should be an array of strings, not numbers or any other type.
  63. HTML font family - the typeface that will be applied by the web browser. The web browser will only be able to apply a font if it is available on the system which it operates. Provide multiple font families, separated by commas, to indicate the preference in which to apply fonts if they aren't available on the system. The Chart Studio Cloud (at https://chart-studio.plotly.com or on-premise) generates images on a server, where only a select number of fonts are installed and supported. These include "Arial", "Balto", "Courier New", "Droid Sans",, "Droid Serif", "Droid Sans Mono", "Gravitas One", "Old Standard TT", "Open Sans", "Overpass", "PT Sans Narrow", "Raleway", "Times New Roman".
  64. Sets the title of the legend group.
  65. Sets the legend rank for this trace. Items and groups with smaller ranks are presented on top/left side while with "reversed"legend.traceorder` they are on bottom/right side. The default legendrank is 1000, so that you can use ranks less than 1000 to place certain items before all unranked items, and ranks greater than 1000 to go after all unranked items.
  66. Sets the width (in px or fraction) of the legend for this trace.
  67. Assigns extra meta information associated with this trace that can be used in various text attributes. Attributes such as trace name, graph, axis and colorbar title.text, annotation text rangeselector, updatemenues and sliders label text all support meta. To access the trace meta values in an attribute in the same trace, simply use %{meta[i]} where i is the index or key of the meta item in question. To access trace meta in layout attributes, use %{data[n[.meta[i]} where i is the index or key of the meta and n is the trace index.
  68. Sets the opacity of the trace.
  69. Reverses the color mapping if true. If true, zmin will correspond to the last color in the array and zmax will correspond to the first color.
  70. Determines whether or not a colorbar is displayed for this trace.
  71. Sets the text elements associated with each z value.
  72. Transposes the z data.
  73. Controls persistence of some user-driven changes to the trace: constraintrange in parcoords traces, as well as some editable: true modifications such as name and colorbar.title. Defaults to layout.uirevision. Note that other user-driven trace attribute changes are controlled by layout attributes: trace.visible is controlled by layout.legend.uirevision, selectedpoints is controlled by layout.selectionrevision, and colorbar.(x|y) (accessible with config: {editable: true}) is controlled by layout.editrevision. Trace changes are tracked by uid, which only falls back on trace index if no uid is provided. So if your app can add/remove traces before the end of the data array, such that the same trace has a different index, you can still preserve user-driven changes if you give each trace a uid that stays with it as it moves.
  74. Determines whether or not this trace is visible. If "legendonly", the trace is not drawn, but can appear as a legend item (provided that the legend itself is visible).
  75. Alternate to x. Builds a linear space of x coordinates. Use with dx where x0 is the starting coordinate and dx the step.
  76. Sets the x coordinates.
  77. Sets a reference between this trace's x coordinates and a 2D cartesian x axis. If "x" (the default value), the x coordinates refer to layout.xaxis. If "x2", the x coordinates refer to layout.xaxis2, and so on.
  78. If "array", the heatmap's x coordinates are given by "x" (the default behavior when x is provided). If "scaled", the heatmap's x coordinates are given by "x0" and "dx" (the default behavior when x is not provided).
  79. Alternate to y. Builds a linear space of y coordinates. Use with dy where y0 is the starting coordinate and dy the step.
  80. Sets the y coordinates.
  81. Sets a reference between this trace's y coordinates and a 2D cartesian y axis. If "y" (the default value), the y coordinates refer to layout.yaxis. If "y2", the y coordinates refer to layout.yaxis2, and so on.
  82. If "array", the heatmap's y coordinates are given by "y" (the default behavior when y is provided) If "scaled", the heatmap's y coordinates are given by "y0" and "dy" (the default behavior when y is not provided)
  83. Sets the z data.
  84. Determines whether or not the color domain is computed with respect to the input data (here in z) or the bounds set in zmin and zmax Defaults to false when zmin and zmax are set by the user.
  85. Sets the upper bound of the color domain. Value should have the same units as in z and if set, zmin must be set as well.
  86. Sets the mid-point of the color domain by scaling zmin and/or zmax to be equidistant to this point. Value should have the same units as in z. Has no effect when zauto is false.
  87. Sets the lower bound of the color domain. Value should have the same units as in z and if set, zmax must be set as well.
  88. Picks a smoothing algorithm use to smooth z data.