Hi @Rony150640,
You need to adjust the plotting margins. Try this code:
help(par)
par()$mai
# [1] 1.02 0.82 0.82 0.42
# From help:
# mai is a numerical vector of the form c(bottom, left, top, right)
# which gives the margin size specified in inches.
# Default settings don't leave enough space for superscripted text
plot(c(1,2,3), c(4,6,8), pch = 20, type = 'b', las = 3,
xlab=bquote("Chl-a (" ~ mgm^-3 ~ ")"),
ylab=bquote("POC (" ~ mgm^-3 ~ ")"),
main='Northeast Monsoon')
# Increase the width of the left margin
par(mai = c(1.02, 1.00, 0.82, 0.42))
par()$mai
# [1] 1.02 1.00 0.82 0.42
# Now plot fits
plot(c(1,2,3), c(4,6,8), pch = 20, type = 'b', las = 3,
xlab=bquote("Chl-a (" ~ mgm^-3 ~ ")"),
ylab=bquote("POC (" ~ mgm^-3 ~ ")"),
main='Northeast Monsoon')
HTH