data = read.table("data.tab")
png("plot.png")
plot(
    data[,1],
    data[,2],
    type="l",
    lty=1,
    log="xy",
    xlim=c(1e-2,1e10),
    xlab="Hydrogen Density [cm⁻³]",
    ylab="Level Population 1D [cm⁻³]"
    )
lines(data[,1],data[,3],lty=2)
abline(v=6.78e5,lty=3)
legend(
    .5,
    1e6,
    legend = c("NLTE Steady State","LTE","Critical Density"),
    lty=c(1,2,3)
#    col=c("blue","green","red")
    )
dev.off()