The minimalist look can be achieved by appending the
following chunk of code to the output object:
+
xlab(NULL) +
ylab(NULL) +
scale_fill_continuous(low = 'green', high = 'red') +
theme(
axis.text = element_blank(),
axis.ticks = element_blank(),
legend.position = 'none',
strip.background = element_blank(),
# strip.text = element_blank(), # useful if only one year of data
plot.background = element_blank(),
panel.background = element_blank(),
panel.border = element_blank(),
panel.grid = element_blank(),
panel.border = element_blank()
)