R/plot-terms.R
    dts_lines_PR.RdAdd lines for the prevalence / parasite rate (PR) from a model of human infection and immunity
dts_lines_PR(tm, PR, nStrata, clrs = "black", llty = 1)the time
the computed parasite rate
the number of human / host population strata
a vector of colors
an integer (or integers) that specifies lty for plotting