a horizontal line at 0 parallel to X-axis.

[zeeshan0112]

I want to draw a a horizontal line at 0 parallel to X-axis.

[FJCC]

I looks like you are using the base plotting function so you would use the abline function to add a line to the plot. Using the h parameter adds a horizontal line with the given y intercept.

DF <- data.frame(X = 1:20, Y = runif(n = 20, min = -5, max = 5))
plot(DF$X, DF$Y)
abline(h = 0)

^{Created on 2020-06-11 by the reprex package (v0.3.0)}

[datavizpyr]

geom_hline() with yintercept will add horizontal line. https://ggplot2.tidyverse.org/reference/geom_abline.html