R: How to join multiple plots into one plot? -

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i have 2 density distribution data , b, want plot 2 density curves 1 plot. used following codes:

plot(user.dens.tas, col="red", xlim=c(0,0.003)) plot(item.dens.tas, col="blue", xlim=c(0,0.003))

how can plot 2 curves 1 plot (combine them)?

enter image description here

plot(user.dens.tas, col="red", xlim=c(0,0.003)) lines(item.dens.tas, col="blue", xlim=c(0,0.003))

puts 1 line in read, other in blue on same plot. might consider adding title , other presentation niceties.

O9