So I set up my graph to be:
ten <- c(0.2,0.16,0.17,0.188)
fifty <- c(0.1,0.24,0.17,0.166)
hundred <- c(0.3,0.16,0.16,0.14)
fiveh <- c(0,0.02,0.04,0.022)
plot(c(10,10,10,10,50,50,50,50,100,100,100,100,500,500,500,500),c(ten,fifty,hundred, fiveh),
ylab= "% of Impaired Rivers", xlab= "Number of Observations", main= "samples from all rivers")
and I'm trying to use abline function to create a trendline in my graph but got confused on how to define my values.
Help on how to make a proper trend line would be greatly appreciated.

