CallierDiverging: Create Diverging Color Palettes with Callier Colors

In patrickreidy/callierr: Color Palettes and Scales for the Callier Center for Communication Disorders

Description

CallierDiverging() creates a diverging color palette. The values on one half of the palette are tints of solarOrange; the values on the other half of the palette are tints of spaceBlue. The endpoints of the palette are solarOrange and spaceBlue. Colors closer to the middle of the palette increase in lightness from the endpoint.

Usage

CallierDiverging(steps = 3, lower = "orange", lightest = 0.85)

Arguments

steps	An integer or list. Default is 3. If steps is an integer, it controls only the number of colors in the palette. If steps is a list, it should comprise character vectors that partition the variable mapped onto the color palette. Furthermore, the elments of the list should be named 'orange', 'blue', or 'gray'.
lower	A character string that must be matched by either 'orange' or 'blue'. Default is 'orange'.
lightest	A numeric between 0 and 1 that denotes the lightness of the lightest tint in the middle of the palatte. Values closer to 0 are darker; those closer to 1 are lighter. Default is 0.85.

Details

A diverging color palette emphasizes: (1) critical values near the middle of the data range and (2) extreme values at both ends of the data range. This is accomplished by concatenating two sequential palettes of different hues; hence, differences above or below the mid-range critical value are represented by a change in hue and differences within either half of the palette are represented by changes in lightness within a fixed hue.

If the argument lower is matched by 'orange', then the lowest value of the diverging palette is solarOrange, and the palette progresses through lightening orange tints, at the low end, and through darkening blue tints, at the high end. If lower is matched by 'blue', then the lowest value of the palette is spaceBlue, and the palette progresses through lightening blue tints, at the low end, and through darkening orange tints, at the high end.

Give some consideration to the type of data that are being represented on the diverging palette and how the structure of that data relates to physical properties of blue and orange hues. (Blue hues have a shorter wavelength and a higher frequency than orange hues.) For example, if the data represented on the diverging palette are (audible) frequencies, then a palette with orange hues on the lower end will parallel the order of the visible frequency scale. Conversely, if the data are distances, then a palette with blue hues on the lower end will parallel the order of the visible wavelength scale.

If the argument steps is an odd integer, then the color in the middle of the palette is the lightest tint of callierGray.

Value

A character vector of hexadecimal codes for colors in the RGB (red-green-blue) color model.

See Also

CallierQualitative, CallierSequential

patrickreidy/callierr documentation built on May 24, 2019, 8:22 p.m.