Color Scale and Palettes

Color Scale

The color scale is a method or function that maps the data values to a group of colors. It transforms a data value in a certain interval(domain) into a color in another color interval(range). Studio provides 3 predefined color scale (or data classification) methods for creating thematic maps:

  1. Quantize (Equal Interval)
  2. Quantile
  3. Jenks Natural Breaks

Users can also create a customized color scale using:

  1. Custom Breaks

In cartography, a thematic map is a type of map that portrays the geographic pattern of a particular subject matter (theme) in a geographic area[1]. There are many different methods to create a thematic map including Choropleth map[2], Isarithmic/Isoline[3], Dot Denstiy map[4], Flow map[5] etc. Color scale or data classification methods can be used to separate the range of values into classes when creating a thematic map.

Quantize (Equal Interval)

Quantize (Equal Interval) scale divides the range of the continuous variable into equal interval bins. The data values are organized into these bins with different colors, which users can specify in color palettes. Quantize scale emphasizes the amount of a data value relative to other values, so it is best applied to data ranges like altitude, precipitation and temperature.

In the "Color Scale" selector, you can select the option "Quantize":

Quantize scale.Quantize scale.

Quantize scale.

Quantile

Quantile scale organizes the data values by grouping them into bins that each have the same number of data values. This method is well suited to linearly distributed data since data values are grouped in equal numbers in each bin. The downside of this approach is that similar values could be placed in different bins, or very different values could be placed in the same bin. One can adjust the number of bins (steps) to minimize the impact of these issues.

The quantile with 4 bins is called "quartile". The quantile with 4 bins is called "quintile".

In the "Color Scale" selector, you can select the option "Quantile":

Quantile scale.Quantile scale.

Quantile scale.

Jenks Natural Breaks

Jenks Natural Breaks is an optimization method that arranges the data values into different groups where the within-group homogeneity is maximized[6]. In essence, it is a clustering algorithm on one-dimensional data to find the best arrangement of data values into different groups. This approach minimizes the variation within each group, so the data within each group are as close as possible in value to each other.

In the "Color Scale" selector, you can select the option "Jenks Natural Breaks":

Jenks Natural Breaks scale.Jenks Natural Breaks scale.

Jenks Natural Breaks scale.

Custom Breaks

Custom Breaks allows the users to specify color scales manually by editing the threshold values and the mapped color class. It also can be used as a tool to adjust the color scales from above methods. There are two major parts in custom breaks panel:

  1. Color Scale Histogram
  2. Custom Breaks Editor

Color Scale Histogram

The color scale histogram is used to represent the distribution of the selected data. In the histogram, the vertical dotted lines at each breakpoint of scale help users to understand how the break values divide the data into different groups. Users can drag and move the ticks to adjust the break values to create a customized color scale easily. The changes made in the histogram are linked with the custom break editor.

Color Scale HistogramColor Scale Histogram

Color Scale Histogram

Custom Breaks Editor

The custom breaks can be edited to specify exact breaks and colors

  • Click 'Custom Breaks' to activate the custom breaks editor
  • Edit break value
  • You can create a new palette, start modifying a copy of an existing palette or supply an array of hex values.
  • Edit color value using a color picker, or input rgb, hex value
  • Add and remove colors
  • Drag to reorder colors

In color scale selector, users can select "Custom Breaks" option to enable custom breaks editing. Then, users can edit custom breaks and color in the custom breaks editor. To save the custom breaks, users can click the "Confirm" button. (See the left figure below).

Edit Custom Breaks (left) Select Color Palette (right).Edit Custom Breaks (left) Select Color Palette (right).

Edit Custom Breaks (left) Select Color Palette (right).

In the custom breaks editor, users can click on each color to pick a new color from the color picker. They can also change color steps (add, remove, or reorder).

To change a predefined color palette, users can click the "Confirm" button to save and close the custom palette editor. Then, click the "Custom Palette" and select one predefined color palette from the dropdown list. (See the right figure above).

When a custom color breaks option is chosen, change steps are disallowed. To change the steps, please enable custom breaks editing and change steps using the custom breaks editor.


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