plot.design function not working on mac

Having trouble getting plot.design to work. Currently taking a course on R and when working through the data packages and examples with code I am not getting the intended results. This is the error code I keep getting. I am running rstudio on a macbook pro.

diatom = read.csv("diatom.csv")
plot.design(diatom)
Error in .plot.des(xf, ydata[, j], fun = fun, ylab = ylab[j], ylim = ylim, :
all columns/components of 'x' must be factors