col2alpha: To use a standard color with an alpha transparency chanel In seqinr: Biological Sequences Retrieval and Analysis

Description

Takes as input a standard R color and an alpha value to return its rgb coding.

Usage

 `1` ```col2alpha(color, alpha = 0.5) ```

Arguments

 `color` A standard R color as in `colors`. `alpha` An alpha transparency value in the interval [0,1].

Value

same as in `rgb`.

Author(s)

J.R. Lobry

`colors`, `col2rgb`, `rgb`.
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29``` ```# # Need alpha transparency channel # par(mar = c(0, 0, 2, 2)+0.1, oma = c(0, 0, 2, 0), mfrow = c(3,2)) for(testcol in c("blue", "red", "green", "yellow", "purple", "darkgreen")){ plot(0,0, type="n", xlim=0:1, ylim = 0:1, axes = FALSE, xlab = "", ylab = "", main = testcol) n <- 11 for(i in seq(0, 1, length = n)){ col <- col2alpha(testcol, i) rect(i, 0, i + 1/n, 1, col = col, border = "black", xpd = NA) text(i+0.5/n, 0.5, round(i,2), xpd = NA) } } mtext("Effect of alpha on some colors\nNote: need alpha transparency channel", side = 3, outer = TRUE) # # The substractive color scheme: # par(mar = c(0,0,3,0)) plot.new() plot.window(xlim = c(-1.5, 1.5), ylim = c(-1,1.75), asp = 1) n <- 10 alpha <- 1/n for(i in 1:(2*n)){ circle(x = -0.5, y = 0, col = col2alpha("yellow", alpha)) circle(x = 0.5, y = 0, col = col2alpha("cyan", alpha)) circle(x = 0, y = 3/4, col = col2alpha("magenta", alpha)) } title("Substractive color scheme\nNote: need alpha transparency channel") ```