[R] plots

[Renalda Munubi-Misinzo]

I would like to have a  plot with values in a reversed order (as shown in
fig 2).  I tried to plot the graph in R using the following codes

plot(density,depth,pch=as.numeric(species),xlab="fish density
(#/m2)",ylab="water depth (m)")

legend(locator(n=1),legend=c("Tropheus brichardi","Petrochromis
kazumbe"),pch=1:2)
unfortunately I can not reverse the axis to get a plot like the one shown
in fig.2 Please can you help me with the codes?

Thanks you