#### Overview of this book

R Graph Essentials
Credits
www.PacktPub.com
Preface
Free Chapter
Base Graphics in R – One Step at a Time
Advanced Functions in Base Graphics
Creating Graphs with ggplot
Index

## Creating axis labels

The first argument in the `axis()` command (the number `1`) specifies the horizontal axis. The `at` argument allows you to specify where to place the axis labels. The vector called `lab` stores the actual labels. Now we create a y axis with horizontal labels, and ticks every four units, using the syntax `at=4*0: yaxismax` as shown:

```axis(2, las=1, at=4*0: yaxismax)
```

Now what does our graph look like?

Now we have included a vertical axis. The argument `las` controls the orientation of the axis labels. Your labels can be either parallel (`las=0`) or perpendicular (`las=2`) to your axis. Using `las=1` ensures horizontal labels, while `las=3` ensures vertical labels.

Now we create a box around the plot and then we add in the two new curves using the `lines()` command, using two different symbol types.

```box()

lines(Y2, pch = 16, type="o", lty=2, col="red")

lines(Y3, pch = 17, type="o", lty=3, col="darkgreen")
```

Let's create a title using the following command:

```title(main="SEVERAL LINE PLOTS", col.main="darkgreen", font.main=2)
```

Now we label the x and y axes using `title()`, along with `xlab` and `ylab`.

```title(xlab=toupper("Letters"), col.lab="purple")

title(ylab="Values", col.lab="brown")
```

Note the `toupper()` command, which always ensures that text within parentheses is uppercase. The `tolower()` command ensures that your text is lowercase.

Finally, we create a legend at the location (`1`, `yaxismax`), though the `legend()` command allows us to position the legend anywhere on the graph (see Chapter 2, Advanced Functions in Base Graphics, for more detail). We include the legend keys using the `c` operator. We control the colors using `col` and ensure that the symbol types match those of the graph using `pch`. To do this job, we include the legend colors in the same logical order in which we created the curves:

```legend(1, yaxismax, c("Y1","Y2", "Y3"), cex=0.7, col=c("blue", "red", "darkgreen"), pch=c(15, 16, 17), lty=1:3)
```

The following is our final plot: