Plot "y" against "x" where "x" is a vector of labels

my.plot.vs.label <- function(x, y, ...)
{ 
    ## Purpose: Plot "y" against "x" where "x" is a vector of labels (string)
    ## Arguments:
    ##   x: a string vector (labels)
    ##   y: a numeric vector or matrix
    ##   ...: passed to "matplot"
    ## Return: a plot
    ## Author: Feiming Chen, Date:  5 Jun 2017, 14:46
    ## ________________________________________________

    s <- seq(x)
    matplot(s, y, type="b", axes = F, xlab ="", ylab="", ...)
    axis(side=2)
    axis(side=1, at=s, labels=x, las=2)

    yn <- ncol(y)
    yna <- names(y)
    if (!is.null(yn) && !is.null(yna)) {
        legend("topright", legend=yna, col=1:yn, lwd=1.5, lty=1:yn)
    }
}
if (F) {                                # Unit Test
    x <- LETTERS
    y <- matrix(rnorm(260), ncol=10)
    my.plot.vs.label(x, y)
    y2 <- as.data.frame(y)
    my.plot.vs.label(x, y2)
}