Colors and color functions

A. Viewing details of a single color palette

When the pal argument of the seecol() function specifies a single color palette, the function plots a more detailed view of this particular color palette:

seecol(pal_unikn)  # view details of pal_unikn 

The detailed overview of a color palette provides us with

• the color names (where available),
  
• their numeric indices (within the color palette),
  
• the HEX values for each color,
  
• the RGB values for each color.

When a color palette contains too many colors, the HEX and RGB values are no longer printed. However, setting hex and rgb to TRUE will force them to be shown.

Note that seecol() also returns the color palette that is being shown. Thus, a typical workflow comprises both seeing a particular color palette and saving it (for storing and applying it later):

my_pal <- seecol(pal_unikn_light)  # view details of AND save a color palette  

Due to saving the color palette (here to my_pal) we can later use it in a visualization:

barplot(1/sqrt(1:10), col = my_pal)  # use my_pal in a plot

Note that seecol() invisibly returns the color palette.
Thus, the following will plot the palette pal_bordeaux without doing anything else with it:

seecol(pal_bordeaux)

but the following would both plot and assign the palette to my_pal:

my_pal <- seecol(pal_bordeaux)

B. Viewing and comparing multiple color palettes

The second mode of seecol() is invoked by providing (a list of) multiple color palettes to its pal argument.
In this case, the function allows comparing these palettes by plotting a color vector for each palette. Some special keywords within the unikn package denote sets of color palettes:

• The keywords "unikn_all", "unikn_basic", pair_all", "pref_all" and "grad_all" refer to University of Konstanz color palettes.

Calling seecol with pal set to these keywords allows comparing pre-defined sets of the color palettes:

Viewing the uni.kn color palettes:

seecol("unikn_all")  # all uni.kn color palettes

1. three basic color palettes:

seecol("unikn_basic")

Note, that pal_unikn_web and pal_unikn_ppt are almost identical, but differ in how vibrant their colors are.

2. three paired color palettes:

seecol("pair_all")

3. all preferred colors from the spectrum and their respective gradients:

seecol("pref_all")

4. only the pre-defined color gradients:

seecol("grad_all")

See the vignette on Institutional colors for creating color palettes for other institutions.

Other seecol() arguments

The seecol() function provides some aesthetic parameters for adjusting how color palettes are plotted:

• col_brd allows specifying the color of box borders (if shown. Default: col_brd = NULL);
  
• lwd_brd allows specifying the line width of box borders (if shown. Default: lwd_brd = NULL);
  
• main and sub allow replacing the default titles with custom titles.

Examples:

seecol("grad_all", col_brd = "black", lwd_brd = .5, main = "Color gradients (with black borders)")

seecol(pal_seegruen, col_brd = "white", lwd_brd = 5, main = "A color palette (with white borders)")

Selecting subsets

Using only a subset of colors:

seecol("unikn_all", n = 4)

seecol(pal_unikn, 4)

Importantly, when using pre-defined color palettes of unikn but a value of n that is smaller than the length of the current color palette, usecol and seecol select a predefined subset of colors:

barplot(1/sqrt(1:2), col = usecol(pal_seeblau, n = 2))
barplot(1/sqrt(1:3), col = usecol(pal_seeblau, n = 3))

Extending color palettes

For values of n that are larger than the number of available colors in pal, the specified color palette is extended using ColorRampPalette:

seecol("unikn_all", n = 12)

Both seecol() and usecol() allow extending or truncating color palettes to a desired number n of colors. For instance:

• Inspecting an extended version of pal_seeblau (with n = 8 colors):

seecol(pal_seeblau, n = 8)

• Using a truncated version of pal_bordeaux (with n = 3 colors):

barplot(1/sqrt(1:9), col = usecol(pal_bordeaux, n = 3))

Mixing colors and color palettes

By passing a vector to pal, we can concatenate 2 color palettes and connect them with a color (here: "white") as the midpoint of a new color palette:

seecol(pal = c(rev(pal_petrol), "white", pal_bordeaux))

We can combine a set of colors and extend this palette by specifying an n argument that is larger than the length of the specified palette:

seecol(pal = usecol(c(Karpfenblau, Seeblau, "gold"), n = 10))

These custom palettes can easily be used in a plot. For instance, we can define and use a subset of the pal_unikn_pair palette as follows:

my_pair <- seecol(pal_unikn_pair, n = 10)

# Create data: 
dat <- matrix(sample(5:10, size = 10, replace = TRUE), ncol = 5)

# Plot in my_pair colors:
barplot(dat, beside = TRUE, col = my_pair)

Creating linear color gradients is also supported by the shades_of() function (see below).

Controlling transparency

Both seecol() and usecol() accept an alpha argument (in a range from 0 to 1) for controlling the transparency of color palettes, with higher values for alpha corresponding to lower transparency (i.e., higher opacity).

Displaying a specific color palette at a medium opacity/transparency:

seecol(pal_unikn, alpha = 0.5)

Setting opacity for a custom color palette:

four_cols <- usecol(c("steelblue", "gold", "firebrick", "forestgreen"), alpha = 2/3)

seecol(four_cols, main = "Four named colors with added transparency")

Setting opacity for comparing of multiple color palettes:

seecol("grad", alpha = 0.67, main = "Seeing transparent color palettes")

Creating and comparing custom palettes

Suppose we want to compare a newly created color palette to existing color palettes. To achieve this, advanced users can use the seecol() function for displaying and comparing different custom palettes. When provided with a list of color palettes as the input to its pal argument, seecol() will show a comparison of the inputs:

# Define 2 palettes: 
pal1 <- c(rev(pal_seeblau), "white", pal_bordeaux)
pal2 <- usecol(c(Karpfenblau, Seeblau, "gold"), n = 10)

# Show the my_pair palette from above, the 2 palettes just defined, and 2 pre-defined palettes:  
seecol(list(my_pair, pal1, pal2, pal_unikn, pal_unikn_pair))

Note that unknown color palettes are named pal_\(n\), in increasing order. Palettes known to seecol() are labeled by their respective names. Labeling only custom palettes works by setting the pal_names argument to a character vector of appropriate length:

seecol(list(my_pair, pal1, pal2, pal_unikn, pal_unikn_pair), 
       pal_names = c("my_pair", "blue_bord", "blue_yell"),
       main = "Labeling custom color palettes")

If the pal_names argument is specified and corresponds to the length of all color palettes, the default names of all color palettes are overwritten by pal_names:

seecol(list(my_pair, pal1, pal2, pal_unikn, pal_unikn_pair), 
       pal_names = c("my_pair", "blue_bord", "blue_yell", "blue_black", "mix_pair"),
       main = "Comparing and labeling custom color palettes")

As before, we can use lower values of n for truncating/obtaining shorter subsets of color palettes:

seecol(list(my_pair, pal1, pal2, pal_unikn, pal_unikn_pair), n = 5)

or higher values of n for extending color palettes:

seecol(list(my_pair, pal1, pal2, pal_unikn, pal_unikn_pair), n = 15)

Finding similar colors with simcol()

Assuming that our favorite color is "deeppink", a good question is: How can we find similar colors? Given some target color, the simcol() function searches through a set of colors to find and return visually similar ones:

simcol("deeppink", plot = FALSE)
#>     deeppink    deeppink2      maroon1      maroon2   violetred1   violetred2 
#>   "deeppink"  "deeppink2"    "maroon1"    "maroon2" "violetred1" "violetred2"

By default, simcol() searches though all named R colors of colors() (of the grDevices package), but adjusting the col_candidates and tol arguments allows for more fine-grained searches:

simcol("deepskyblue", col_candidates = pal_seeblau, tol = c(50, 50, 100))
#>   deepskyblue      seeblau3      seeblau4      seeblau5 
#> "deepskyblue"     "#59C7EB"     "#00A9E0"     "#008ECE"

Finding color names with grepal()

We often search for some particular color hue (e.g., some sort of purple), but also know that the particular color named “purple” is not the one we want. Instead, we would like to see all colors that contain the keyword “purple” in its name. The grepal() function addresses this need:

grepal("purple")  # get & see 10 names of colors() with "purple" in their name