Plotting math in R can be acheived using the expression(). To know detailed usage, in R console,
But expression() is not flexible when you want to plot math symbols and parameters altogether. In this case, we use bquote() which is actually a wraper for substitute() and quote(). It has the ability to do paste() and expression() altogether. Here is a simple example.
k <- 2
plot(1, main=bquote(y[i][","][j]~"= "*.(k)))
Note, ".()" evaluates whatever inside the parenthesis. In the expression() and bquote(), "~"means a single-bye space. To bind two expression together without space, use "*" instead.
14 hours ago