How to specify the actual x axis values to plot as x axis ticks in R

I am creating a plot in R and I dont like the x axis values being plotted by R.

For example:

x <- seq(10,200,10)
y <- runif(x)

plot(x,y)

This plots a graph with the following values on the X axis:

50, 100, 150, 200

However, I want to plot the 20 values 10,20, 30 ... 200 stored in variable x, as the X axis values. I have scoured through countless blogs and the terse manual - after hours of searching, the closest I've come to finding anything useful is the following (summarized) instructions:

1. call plot() or par(), specifying argument xaxt='n'
2. call axis() e.g. axis(side = 1, at = seq(0, 10, by = 0.1), labels = FALSE, tcl = -0.2)

I tried it and the resulting plot had no x axis values at all. Is it possible that someone out there knows how to do this? I can't believe that no one has ever tried to do this before.

You'll find the answer to your question in the help page for ?axis.

Here is one of the help page examples, modified with your data:

Option 1: use xaxp to define the axis labels

plot(x,y, xaxt="n")
axis(1, xaxp=c(10, 200, 19), las=2)

Option 2: Use at and seq() to define the labels:

plot(x,y, xaxt="n")
axis(1, at = seq(10, 200, by = 10), las=2)

Both these options yield the same graphic:

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PS. Since you have a large number of labels, you'll have to use additional arguments to get the text to fit in the plot. I use las to rotate the labels.

Take a closer look at the ?axis documentation. If you look at the description of the labels argument, you'll see that it is:

"a logical value specifying whether (numerical) annotations are 
to be made at the tickmarks,"

So, just change it to true, and you'll get your tick labels.

x <- seq(10,200,10)
y <- runif(x)
plot(x,y,xaxt='n')
axis(side = 1, at = x,labels = T)
# Since TRUE is the default for labels, you can just use axis(side=1,at=x)

Be careful that if you don't stretch your window width, then R might not be able to write all your labels in. Play with the window width and you'll see what I mean.

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It's too bad that you had such trouble finding documentation! What were your search terms? Try typing r axis into Google, and the first link you will get is that Quick R page that I mentioned earlier. Scroll down to "Axes", and you'll get a very nice little guide on how to do it. You should probably check there first for any plotting questions, it will be faster than waiting for a SO reply.

Hope this coding will helps you :)

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

axis(side=1,at=c(1,20,30,50),labels=c("1975","1980","1985","1990"))

In case of plotting time series, the command ts.plot requires a different argument than xaxt="n"

require(graphics)
ts.plot(ldeaths, mdeaths, xlab="year", ylab="deaths", lty=c(1:2), gpars=list(xaxt="n"))
axis(1, at = seq(1974, 1980, by = 2))