ggplot2 in R
We devise visualizations on mtcars dataset which includes 32 car brands and 11 attributes using ggplot2 layers.
Data Layer:
ggplot2 in R the data Layer we define the source of the information to be visualize, let’s use the mtcars dataset in the ggplot2 package.
R
library (ggplot2) library (dplyr) ggplot (data = mtcars) + labs (title = "MTCars Data Plot" ) |
Output:
Aesthetic Layer:
ggplot2 in R Here we will display and map dataset into certain aesthetics.
R
# Aesthetic Layer ggplot (data = mtcars, aes (x = hp, y = mpg, col = disp))+ labs (title = "MTCars Data Plot" ) |
Output:
Geometric layer:
ggplot2 in R geometric layer control the essential elements, see how our data being displayed using point, line, histogram, bar, boxplot.
R
# Geometric layer ggplot (data = mtcars, aes (x = hp, y = mpg, col = disp)) + geom_point () + labs (title = "Miles per Gallon vs Horsepower" , x = "Horsepower" , y = "Miles per Gallon" ) |
Output:
Geometric layer: Adding Size, color, and shape and then plotting the Histogram plot
R
# Adding size ggplot (data = mtcars, aes (x = hp, y = mpg, size = disp)) + geom_point () + labs (title = "Miles per Gallon vs Horsepower" , x = "Horsepower" , y = "Miles per Gallon" ) # Adding shape and color ggplot (data = mtcars, aes (x = hp, y = mpg, col = factor (cyl), shape = factor (am))) + geom_point () + labs (title = "Miles per Gallon vs Horsepower" , x = "Horsepower" , y = "Miles per Gallon" ) # Histogram plot ggplot (data = mtcars, aes (x = hp)) + geom_histogram (binwidth = 5) + labs (title = "Histogram of Horsepower" , x = "Horsepower" , y = "Count" ) |
Output:
Facet Layer:
ggplot2 in R facet layer is used to split the data up into subsets of the entire dataset and it allows the subsets to be visualized on the same plot. Here we separate rows according to transmission type and Separate columns according to cylinders.
R
# Facet Layer # Separate rows according to transmission type p <- ggplot (data = mtcars, aes (x = hp, y = mpg, shape = factor (cyl))) + geom_point () p + facet_grid (am ~ .) + labs (title = "Miles per Gallon vs Horsepower" , x = "Horsepower" , y = "Miles per Gallon" ) # Separate columns according to cylinders p <- ggplot (data = mtcars, aes (x = hp, y = mpg, shape = factor (cyl))) + geom_point () p + facet_grid (. ~ cyl) + labs (title = "Miles per Gallon vs Horsepower" , x = "Horsepower" , y = "Miles per Gallon" ) |
Output:
Statistics layer
ggplot2 in R this layer, we transform our data using binning, smoothing, descriptive, intermediate
R
ggplot (data = mtcars, aes (x = hp, y = mpg)) + geom_point () + stat_smooth (method = lm, col = "red" ) + labs (title = "Miles per Gallon vs Horsepower" ) |
Output:
Coordinates layer:
ggplot2 in R these layers, data coordinates are mapped together to the mentioned plane of the graphic and we adjust the axis and changes the spacing of displayed data with Control plot dimensions.
R
ggplot (data = mtcars, aes (x = wt, y = mpg)) + geom_point () + stat_smooth (method = lm, col = "red" ) + scale_y_continuous ( "Miles per Gallon" , limits = c (2, 35), expand = c (0, 0)) + scale_x_continuous ( "Weight" , limits = c (0, 25), expand = c (0, 0)) + coord_equal () + labs (title = "Miles per Gallon vs Weight" , x = "Weight" , y = "Miles per Gallon" ) |
Output:
Coord_cartesian() to proper zoom in:
R
# Add coord_cartesian() to proper zoom in ggplot (data = mtcars, aes (x = wt, y = hp, col = am)) + geom_point () + geom_smooth () + coord_cartesian (xlim = c (3, 6)) |
Output:
Theme Layer:
ggplot2 in R layer controls the finer points of display like the font size and background color properties.
Example 1: Theme layer – element_rect() function
R
ggplot (data = mtcars, aes (x = hp, y = mpg)) + geom_point () + facet_grid (. ~ cyl) + theme (plot.background = element_rect (fill = "blue" , colour = "gray" )) + labs (title = "Miles per Gallon vs Horsepower" ) |
Output:
Example 2:
R
ggplot (data = mtcars, aes (x = hp, y = mpg)) + geom_point () + facet_grid (am ~ cyl) + theme_gray ()+ labs (title = "Miles per Gallon vs Horsepower" ) |
Output:
ggplot2 in R provides various types of visualizations. More parameters can be used included in the package as the package gives greater control over the visualizations of data. Many packages can integrate with the ggplot2 package to make the visualizations interactive and animated.
Contour plot for the mtcars dataset
R
# Install and load required packages install.packages ( "ggplot2" ) library (ggplot2) # Create a 2D density contour plot for the mtcars dataset ggplot (mtcars, aes (x = wt, y = mpg)) + stat_density_2d ( aes (fill = ..level..), geom = "polygon" , color = "white" ) + scale_fill_viridis_c () + labs (title = "2D Density Contour Plot of mtcars Dataset" , x = "Weight (wt)" , y = "Miles per Gallon (mpg)" , fill = "Density" ) + theme_minimal () |
Output:
In
ggplot2 in R stat_density_2d
to generate the 2D density contour plot. The aesthetics x
and y
specify the variables on the x-axis and y-axis, respectively. The fill aesthetic is set to ..level..
to map fill color to density levels.
Creating a panel of different plots
R
library (ggplot2) library (gridExtra) # Selecting specific columns from mtcars dataset selected_cols <- c ( "mpg" , "disp" , "hp" , "drat" ) selected_data <- mtcars[, selected_cols] # Create histograms for individual variables hist_plot_mpg <- ggplot (selected_data, aes (x = mpg)) + geom_histogram (binwidth = 2, fill = "blue" , color = "white" ) + labs (title = "Histogram: Miles per Gallon" , x = "Miles per Gallon" , y = "Frequency" ) hist_plot_disp <- ggplot (selected_data, aes (x = disp)) + geom_histogram (binwidth = 50, fill = "red" , color = "white" ) + labs (title = "Histogram: Displacement" , x = "Displacement" , y = "Frequency" ) hist_plot_hp <- ggplot (selected_data, aes (x = hp)) + geom_histogram (binwidth = 20, fill = "green" , color = "white" ) + labs (title = "Histogram: Horsepower" , x = "Horsepower" , y = "Frequency" ) hist_plot_drat <- ggplot (selected_data, aes (x = drat)) + geom_histogram (binwidth = 0.5, fill = "orange" , color = "white" ) + labs (title = "Histogram: Drat" , x = "Drat" , y = "Frequency" ) # Arrange the plots in a grid grid.arrange (hist_plot_mpg, hist_plot_disp, hist_plot_hp, hist_plot_drat, ncol = 2) |
Output:
The ggplot2
and gridExtra
packages to create histograms for four different variables (“Miles per Gallon,” “Displacement,” “Horsepower,” and “Drat”) from the mtcars
dataset.
Each histogram is visually represented in a distinctive color (blue, red, green, and orange) with white borders. The resulting grid of histograms provides a quick visual overview of the distribution of these car-related variables.
Save and extract R plots:
To save and extract plots in R, you can use the ggsave function from the ggplot2 package. Here’s an example of how to save and extract plots:
R
# Create a plot plot <- ggplot (data = mtcars, aes (x = hp, y = mpg)) + geom_point () + labs (title = "Miles per Gallon vs Horsepower" ) # Save the plot as an image file (e.g., PNG) ggsave ( "plot.png" , plot) # Save the plot as a PDF file ggsave ( "plot.pdf" , plot) # Extract the plot as a variable for further use extracted_plot <- plot plot |
Output:
In this demonstration, I used ggplot to construct a plot and the ggsave function to save it as a PDF file (plot.pdf) and a PNG image file (plot.png). By including the correct file extension, you can indicate the intended file format.
You may easily give the ggplot object to a variable, as demonstrated with extracted_plot, to extract the plot as a variable for later usage.
Be sure to substitute your unique plot and desired file names for the plot code and file names (plot.png and plot.pdf).
Data visualization with R and ggplot2
Data visualization with R and ggplot2 in R Programming Language also termed as Grammar of Graphics is a free, open-source, and easy-to-use visualization package widely used in R Programming Language. It is the most powerful visualization package written by Hadley Wickham.
It includes several layers on which it is governed. The layers are as follows:
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