Plot multiple lines together using "matplot"

my.line.plot  <- function(x, y, ...)
{ 
    ## Purpose: Template function for making lines by group. 
    ## Arguments:
    ##   x: X-coords
    ##   y: a matrix with Y-coords (each column has a set of Y values)
    ##   ...: passed to "plot"
    ## Return: A plot assuming log X-axis with axes tickes given by "x". 
    ## Author: Feiming Chen, Date:  9 Feb 2017, 14:02
    ## ________________________________________________n
    N <- ncol(y)                        # number of lines
    matplot(x, y, type="b", log="x", xaxt="n", lwd=2, lty=seq(N), col = rainbow(N), ...)  
    matpoints(x, y, log="x", xaxt="n", col = "black", ...)
    axis(1, at=x)
}
if (F) {                                # Unit Test
    x <- c(0.1, 1, 10)
    y <- matrix(rnorm(9), 3)
    my.line.plot(x, y, xlab="Tiime", ylab="Signal", main="Line Plot by Groups")
}