Adding Tick Marks to a Custom Axis
# 14.6a Tick marks ======================================================= 14.6a
png(filename = "illustrations/fig-14-10-ticks-BW.png",
units = "in", # Set measurements in inches
res = 1200, # Set resolution at 1200dpi
width = 6, # Width at 6 inches
height = 4) # Height at 4 inches
par(mai = c(3.5, .25, .25, .25)) # Set margin sizes in inches
plot(myV1, myV2, type = "n", # Setup w/no points & default x axis
xlab = NA, # Turn off x axis label
ylab = NA, # Turn off y axis label
yaxt = "n", # Turn off y axis
xlim = c(0, 10)) # Set x axis range
axis(side = 1, # New x axis
at = c(0:10), # Ticks at 0-10
line = 3) # Move axis down to 3rd line
axis(side = 1, # New x axis
at = c(seq(0, 10, by = 2)), # Major ticks at 0-10 by 2
labels = LETTERS[1:6], # A-F as labels
line = 6) # Put axis on 6th line
axis(side = 1, # New x axis
at = c(seq(1, 10, by = 2)), # Minor ticks at 1-10 by 2
labels = NA, # Turn off labels for minor ticks
line = 6) # Overlay axis on 6th line
axis(side = 1, # New x axis
at = c(0:10), # Major ticks at 0-10
labels = c(1990:2000), # Use years for labels
las = 2, # Rotate labels to be perpendicular
col = gray(.5), # Set main axis line to med gray
tcl = -.75, # Major tick length at .75 below line
col.tick = "black", # Make major ticks black
lwd = 2, # Make major ticks longer
line = 9) # Put axis on 9th line below plot
axis(side = 1, # Add overlay axis for the minor ticks
at = c(seq(.5, 10, by = 1)), # Minor ticks at every .5
labels = NA, # No labels for minor ticks
tcl = -.3, # Minor ticks length is .3 below line
lwd = 0, # Turn off main axis line for overlay
lwd.ticks = 1.25, # Set minor tick width to 1.25
col.tick = "darkgray", # Color for minor tick marks
line = 9) # Overlay axis on 9th line
axis(side = 1, # New x axis
at = c(0:10), # Major ticks at 0 - 10
labels = NA, # Turn off labels
tcl = -.5, # Major tick length at .5 below line
lwd = 1.25, # Make major ticks thicker
line = 13) # Put axis on 13th line
text(x = seq(0.3, 10.3, 1), # x values for axis labels
y = -46, # y value for axis labels
xpd = TRUE, # Allow writing outside plot area
labels = as.character(c(1990:2000)), # Years as text labels
pos = 2, # Left align labels
srt = 45) # Rotate strings 45 degrees
dev.off() # Output png file