R Glittery error "X11 font -adobe-helvetica-% s-% s - * - * -% d - * - * - * - * - * - * - *, face 1 size 9 cannot be loaded"

I am programming in R and trying to display a graph using ggplot.

But I am getting:

Error: X11 font -adobe-helvetica-% s-% s ---% d ------- *, face 1 at size 9 cannot be loaded

I am working on Ubuntu 16.04

Error image