Create Boxplot with respect to two factors using ggplot2 in R
Multiple variable distributions can be visualized with boxplots. ggplot2 allows us to create beautiful boxplots quickly. It is possible to have multiple subgroups for a variable of interest. In those situations, it is very useful to visualize using “grouped boxplots”. The ggplot2 package in R programming language provides a number of options for visualizing such grouped boxplots.
Now talking about Boxplot, then each boxplot is created for every category or level in that factor that is represented by a factor and a numerical column. geom_boxplot also allows us to plot both factors using the fill argument when there are two factors. Geom_boxplot() is the key function
Syntax:
geom_boxplot(width,notch,color,size,linetype, fill,outliner.color, outliner.size, outliner.shape)
Parameter:
- width: width of the boxplot
- notch: if it is true then it will create a notched boxplot and notches are used to compare boxplots.
- color, size,line type: borderline, color, size and shape.
- fill: used to fill box plot areas.
- outlier.colour, outlier.shape, outlier.size: The color, the shape and the size for outlying points.
Now let us look at a few implementations.
Example 1:
R
# create a Data FrameGender<-sample(c("Male","Female"),20,replace=TRUE)Values<-rnorm(20,mean=0,sd=1)Group<-sample(letters[1:5],20,replace=TRUE)df<-data.frame(Gender,Values,Group)library(ggplot2)# creating a boxplotggplot(df,aes(Gender,Values))+geom_boxplot(aes(fill=Group)) |
Output:
Create a boxplot with respect to two factors using ggplot2
Example 2:
R
# load ggplot2 package if already installedlibrary(ggplot2)# create a data frame with two factors df <- data.frame(Factor1=factor(rbinom(30, 1, 0.55), label=c("male","female")), Factor2=factor(rbinom(30, 1, 0.45), label=c("young","old")), Values=rnorm(30,mean=5,sd=2))# Now make a interaction between two factors # on x axis df$Factor1Factor2 <- interaction(df$Factor1, df$Factor2) # now Plot Boxplot with fill color according# to factor1 and factor2ggplot(aes(y = Values, x = Factor1Factor2), data = df) + geom_boxplot(aes(fill=Factor1Factor2)) |
Output:
Create Boxplot with respect to two factors using ggplot2
Example 3:
R
# Load ggplot2 package if already installedlibrary(ggplot2)# Create a data frame with two factorsdf <- data.frame( Factor1 = factor(rbinom(30, 1, 0.55), label = c("male", "female")), Factor2 = factor(rbinom(30, 1, 0.45), label = c("young", "old")), Values = rnorm(30, mean = 5, sd = 2))# Create an interaction between the two factorsdf$Factor1Factor2 <- interaction(df$Factor1, df$Factor2)# Define custom colors for the fillcustom_colors <- c("steelblue", "darkorange", "forestgreen", "firebrick")# Plot the box plot with custom aestheticsggplot(df, aes(x = Factor1Factor2, y = Values, fill = Factor1Factor2)) + geom_boxplot(width = 0.5, alpha = 0.7, outlier.shape = NA) + geom_jitter(width = 0.2, height = 0, size = 3, alpha = 0.8) + scale_fill_manual(values = custom_colors) + labs(x = "Factor 1 & Factor 2", y = "Values") + ggtitle("Box Plot with Factor 1 & Factor 2") + theme_minimal() + theme( plot.title = element_text(size = 16, face = "bold"), axis.text = element_text(size = 12), axis.title = element_text(size = 14, face = "bold"), legend.title = element_blank(), legend.position = "none" ) |
Output:
Create boxplot with respect to two factors using ggplot2
- Custom colors (custom_colors) use to establish the boxes’ fill. we can change these colors to suit our tastes or go with a whole other palette.
- To overlay individual data points on top of the boxes, geom_jitter was added. This gives an idea of how the data is distributed.
- Utilizing the geom_boxplot options, the boxes’ width, alpha (transparency), and outlier form were changed.
- added more plot components, such as axis labels and a plot title, and changed the theme to a simple design.
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