Replace X-axis with own values

I have a question regarding the command plot().

Is there a way to fully eliminate the x-axis and replace it with own values? I know that I can get rid of the axis by doing

plot(x,y, xaxt = 'n')

and then add an axis with

axis(side = 1 etc.)

However, when I add the axis, obviously it still refers to the data plotted as 'x'. I would only like to plot the 'y'-values and add the x-axis my own in the sense of just "drawing" the x-axis with own values specified. Is there any way to do that?

The background of this question is that my two data frames differ in their length and therefore I cannot plot them.

Not sure if it's what you mean, but you can do this:

plot(1:10, xaxt = "n", xlab='Some Letters')
axis(1, at=1:10, labels=letters[1:10])

which then gives you the graph:

You could set labels = FALSE inside axis(...) and then print the labels in a separate command using text(...). This option would allow you to rotate the text in case you need it.

lablist<-as.vector(c(1:10))
axis(1, at=seq(1, 10, by=1), labels = FALSE)
text(seq(1, 10, by=1), par("usr")[3] - 0.2, labels = lablist, srt = 45, pos = 1, xpd = TRUE)

Detailed explanation here