Adding the sample name to the end of the plotted spectra

label_specs.R

data(sicalis)

# plot the desired spectra, leaving room horizontally to add labels

plot(sicalis, select=2:4, xlim=c(300,800))

# find the y position to add the labels right where they finish (wavelength=700)
# using nrow to select the last row (for the last wavelength value)

# subset the last wavelength value (column 1)
xpos <- sicalis[nrow(sicalis), 1]
xpos

# subset the last reflectance value for the spectra I want to label
ypos <- sicalis[nrow(sicalis), 2:4]
ypos

# add the labels
# pos=4 will put the text to the right of the specified coordinate
#
# IMPORTANT: the actual relative size of the text will depend on your resolution and how
# you're exporting, so you might need to tweak the text() command a bit

labels <- c('crown', 'throat', 'belly')

text(xpos, ypos, labels, pos=4)

##
# if you want to make it "prettier"
##

plot(sicalis, select=2:4, 
  xlim=c(300,750), col=spec2rgb(sicalis), xaxt='n')
axis(1, at=seq(300, 700, by=100))
text(xpos, ypos, labels, pos=4)