# Visible light spectrum
# Michael Minn
# 29 August 2020

frequencies = list(
	c("ultraviolet", 800, "#000000"),
	c("violet", 750, "#804080"),
	c("indigo", 675, "#400080"),
	c("blue", 630, "#00FFFF"),
	c("green", 590, "#008000"),
	c("yellow", 525, "#FFFF00"),
	c("orange", 500, "#FF8000"),
	c("red", 460, "#800000"),
	c("infrared", 380, "#000000"))

frequencies = data.frame(t(data.frame(frequencies, stringsAsFactors=F)), stringsAsFactors=F)
rownames(frequencies) = frequencies[,1]
frequencies = cbind(frequencies, t(col2rgb(frequencies[,3])))

colnames(frequencies) = c("name", "thz", "hex", "red", "green", "blue")

frequencies$thz = as.numeric(frequencies$thz)

red = approxfun(frequencies$thz, as.numeric(frequencies$red) / 256)
green = approxfun(frequencies$thz, as.numeric(frequencies$green) / 256)
blue = approxfun(frequencies$thz, as.numeric(frequencies$blue) / 256)

png("2020-visible-light-spectrum.png", width=500, height=400, pointsize=14)

par(mar=c(1,1,1,1))
plot(0, 0, xlim=c(0,10), ylim=c(0,11), col="white", axes=F, xlab=NA, ylab=NA)

for (thz in seq(min(frequencies$thz), max(frequencies$thz), 0.5)) {
	y = 10 * (thz - min(frequencies$thz)) / diff(range(frequencies$thz))
	lines(x = c(1.5, 4.5), y = c(y, y), lwd=1, col=rgb(red(thz), green(thz), blue(thz)))
}

y = 10 * (frequencies$thz - min(frequencies$thz)) / diff(range(frequencies$thz))
text(0, y, frequencies$thz, pos=4)
text(5, y, frequencies$name, pos=4)
text(7, y, ifelse(frequencies$hex == "#000000", "(not visible)", frequencies$hex), pos=4)

text(0, 11, "Frequency (Thz)", pos=4, font=2)
text(5, 11, "Name", pos=4, font=2)
text(7, 11, "RGB Hex Code", pos=4, font=2)

dev.off()