Remove axis labels from a plot in R after the plot has already been created

Question

I am using the plot function of a particular package, namely the SPEI library. This function does not appear to accept any parameters to change the way the plot looks when it is generated.

I would like to know how to remove axis values, add new ones, and (ideally) rename the x-axis after the plot has already been created.

Please note that I have seen the other similar topics (e.g: Remove plot axis values) and they are not applicable to my situation. I know that when calling the base plot functions in R, you can set xaxt = "n", axes= FALSE, etc.

Here is a quick version of what I mean:

library(SPEI)
data(wichita)
x <- spei(wichita[,'PRCP'], 1) 
plot.spei(x, main = "Here's a plot")
plot.spei(x, main = "Also a plot", xaxt = "n") #Note that xaxt does not affect output

Answer 1

That function uses base graphics and does not allow for any parameter to be passed through the function. There is no way to remove the x-axis labels without editing the function. Here's a way to make a copy and change just the one line that needs to be edited. (Note, since this method uses line numbers it's pretty fragile, this was tested with SPEI_1.7)

my_plot_spei <- plot.spei
my_plot_spei_body <- as.list(body(my_plot_spei))
my_plot_spei_body[[c(14,4,5)]] <- quote(plot(datt, type = "n", xlab = "", ylab = label, main = main[i], ...))
body(my_plot_spei) <- as.call(my_plot_spei_body)

then this will work

x <- spei(wichita[,'PRCP'], 1) 
my_plot_spei(x, main = "Here's a plot", xaxt="n")