# [R] CIE Diagram with wavelengths tick marks

Kenneth Knoblauch ken@knob|@uch @end|ng |rom |n@erm@|r
Thu Jul 20 14:42:54 CEST 2023

```Hi,

I'm assuming that by CIE Diagram, you mean the 1931 2 deg standard.  Tables of these (and other CIE standards) can be found at the site http://www.cvrl.org maintained by Andrew Stockman.  You can find and download these classic CIE data and more modern versions from there.

Since you have plotted the spectrum locus of the chromaticity diagram (I'm supposing), you ought to be able to just pick off the wavelengths that you want and add a small point or a small line as a tick mark.  If you want it oriented, you'll have to do a little calculation to get the direction perpendicular to the spectrum locus at each wavelength, but that's not too complicated.

I recently needed a figure for a talk and downloaded the 2 deg 1931 data from the above website and used points to indicate specific wavelengths that interested me.  The code is below:

names(d) <- c("Wavelength", "X", "Y", "Z")
d\$x <- with(d, X/(X + Y + Z))
d\$y <-  with(d, Y/(X + Y + Z))

par(pty = "s")
plot(y ~ x, d, type = "l", axes = 'FALSE',
xlim = c(0, 1), ylim = c(0, 1))
lines(y[c(1, nrow(d))]~ x[c(1, nrow(d))], d)
axis(1, seq(0, 1, 0.2))
axis(2, seq(0, 1, 0.2))
lines(c(0, 1), c(1, 0), col = "blue", lwd = 2, lty = 2)

points(d[d\$Wavelength == 555, ]\$x, d[d\$Wavelength == 555, ]\$y, pch = 16, col = "green")
points(d[d\$Wavelength == 589, ]\$x, d[d\$Wavelength == 589, ]\$y, pch = 16, col = "yellow")
points(d[d\$Wavelength == 670, ]\$x, d[d\$Wavelength == 670, ]\$y, pch = 16, col = "red")

Good luck.

best,

Ken

# Hy,

# for plotting CIE Diagrams i found Package pavo with function cieplot.
# That works fine.
# Now i want to have wavelength tick marks as well around the plotting area.
# Is there a way to do so, also other ways/Pakages to plot are welcome.

# My sample Code:
# library(pavo)

# coldat2 <- as.data.frame(matrix(rep(1/3, 3), nrow = 1, ncol = 3))

# # Make sure this dataset works with the cieplot() function
# attr(coldat2, "clrsp") <- "CIEXYZ"
# colnames(coldat2) <- c("x", "y", "z")

# cieplot(coldat2, col="white", main="CIE Test Plot")

# Best regards
# Tilmann

___
Kenneth Knoblauch
Inserm U1208
Stem-cell and Brain Research Institute
18 avenue du Doyen Lépine
69500 Bron
France
tel: +33 (0)4 72 91 34 77
fax: +33 (0)4 72 91 34 61
portable: +33 (0)6 84 10 64 10
https://sbri.fr/public-profile/63/single-member/

```