When creating barplots in R, we often want to add text to our charts to provide more context and information. This can be easily achieved with the help of HTML tags formatting. In this article, we will explore how to add text to a horizontal barplot in R with the Y-axis at a different scale.
First, let's create a basic horizontal barplot using the "mtcars" dataset. We will be using the "mpg" variable as our Y-axis and the "gear" variable as our bar categories.
```{r}
# Load the dataset
data(mtcars)
# Create a horizontal barplot
barplot(mtcars$mpg, names.arg = mtcars$gear, horiz = TRUE, col = "steelblue")
```
As you can see, our barplot only contains the Y-axis labels and the bar categories. Let's say we want to add the average MPG value for each gear category as text on top of the bars. To do this, we will use the "text" function and specify the coordinates for our text.
```{r}
# Add text to the plot
text(x = mtcars$mpg, y = mtcars$gear, labels = mtcars$mpg, pos = 4, cex = 0.8)
```
This adds the numerical values as text on top of the bars, but it may not be as visually appealing as we want it to be. This is where HTML tags formatting comes in. We can use HTML tags to format our text and make it more presentable.
Let's add HTML tags to our text function to change the font size, color, and alignment.
```{r}
# Add text with HTML tags
text(x = mtcars$mpg, y = mtcars$gear, labels = paste("<span style='font-size: 12pt; color: #FFFFFF; text-align: center;'>", mtcars$mpg, "</span>", sep = ""), pos = 4)
```
In this code, we have used the "paste" function to add our HTML tags to the text. We have also specified the font size, color, and alignment using the "style" attribute. Now our text stands out on the barplot and is more readable.
But what if we want to add the text on the Y-axis at a different scale? This is where we need to make some changes to our code. We will use the "axis" function to add a second Y-axis and specify the scale we want.
```{r}
# Create a secondary Y-axis
axis(4, at = mtcars$gear, labels = paste("<span style='font-size: 12pt; color: #FFFFFF; text-align: center;'>", mtcars$mpg, "</span>", sep = ""))
```
As you can see, we have used the "axis" function to create a secondary Y-axis on the right side of our plot. We have also used the same HTML tags formatting as before to format our text. Now our plot looks like this:
```{r}
# Create a horizontal barplot with a secondary Y-axis
barplot(mtcars$mpg, names.arg = mtcars$gear, horiz = TRUE, col = "steelblue")
text(x = mtcars$mpg, y = mtcars$gear, labels = paste("<span style='font-size: 12pt; color: #FFFFFF; text-align: center;'>", mtcars$mpg, "</span>", sep = ""), pos = 4)
axis(4, at = mtcars$gear, labels = paste("<span style='font-size: 12pt; color: #FFFFFF; text-align: center;'>", mtcars$mpg, "</span>", sep = ""))
```
Now we have successfully added text to our horizontal barplot with the Y-axis at a different scale. This technique can also be applied to other types of plots in R, such as line charts, scatter plots, and more.
In conclusion, using HTML tags formatting in R allows us to add more customization and visual appeal to our plots. With a few simple changes to our code, we can add text to our barplots at different scales and make our charts more informative and visually appealing. So next time you create a barplot in R, don't forget to add some HTML tags to make it stand out.
