Creating a smooth color ramp across a range of values

Cartographica has some powerful tools for creating and manipulating styles and for applying color palettes to a set of styles.   This tip is about using these functions to create a smooth ramp across a range of values, without having to determine exactly how many steps to add.   This is intended for use with relatively small (<256 feature) lists, such as provinces or counties, and values that are unlikely to be repeated, such as population or area.

  1. Double-click on your layer to open the Styles window
  2. Make sure you have a column selected in Based On
  3. Choose Distribute Unique Values from the gear menu   
    This will create a single sub-style for  each individual value in the list.    We won't be directly using these, this is just to approximate the number of styles we need to represent the data well.
  4. Choose Distribute Equal Intervals from the gear menu
    This will redistribute across the entire range based on an equal number of weightings from lowest to highest.
  5. Choose Window > Show Color Palettes to display the color options
  6. Drag a suitable color palette from the Color Palettes window to your style list

This creates a relatively good ramp without having to manually create every entry.  If you have a much larger set of values, it is better to manually create the number of styles you need to step the value correctly and then follow steps 4-6.

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