A useful way to convey a collection of summary statistics in a dataset is through the use of a box plot. This type of graph depicts a dataset's minimum and maximum, as well as its lower, median, and upper quartiles in a single diagram. Let us look at how box plots are created in R:
- Use the
boxplot(...)function to create a box plot.> #create a box plot that depicts the number of soldiers required to launch a fire attack > #get the data to be used in the plot > boxplotFireShuSoldiersData <- subsetFire$ShuSoldiers > #customize the plot > boxPlotFireShuSoldiersLabelMain <- "Number of Soldiers Required to Launch a Fire Attack" > boxPlotFireShuSoldiersLabelX <- "Fire Attack Method" > boxPlotFireShuSoldiersLabelY <- "Number of Soldiers" > #use boxplot(...) to create and display the box plot > boxplot(x = boxplotFireShuSoldiersData, main = boxPlotFireShuSoldiersLabelMain, xlab = boxPlotFireShuSoldiersLabelX, ylab = boxPlotFireShuSoldiersLabelY)
- Your plot will be displayed in the graphic window, as shown in the following:
- Use the
boxplot(...)function to create a box plot that compares multiple datasets.> #create a box plot that compares the number of soldiers required across the battle methods > #get the data formula to be used in the plot > boxplotAllMethodsShuSoldiersData <- battleHistory$ShuSoldiers ~ battleHistory$Method > #customize the plot > boxPlotAllMethodsShuSoldiersLabelMain <- "Number of Soldiers Required by Battle Method" > boxPlotAllMethodsShuSoldiersLabelX <- "Battle Method" > boxPlotAllMethodsShuSoldiersLabelY <- "Number of Soldiers" > #use boxplot(...) to create and display the box plot > boxplot(formula = boxplotAllMethodsShuSoldiersData, main = boxPlotAllMethodsShuSoldiersLabelMain, xlab = boxPlotAllMethodsShuSoldiersLabelX, ylab = boxPlotAllMethodsShuSoldiersLabelY)
- Your plot will be displayed in the graphic window, as shown in the following:
We just created two box plots using R's boxplot(...) function, one with a single box and one with multiple boxes.
We started by generating a single box plot that was composed of a dataset, main title, and x and y labels. The basic format for a single box plot is as follows:
boxplot(x = dataset)
The x argument contains the data to be plotted. Technically, only x is required to create a box plot, although you will often include additional arguments. Our boxplot(...) function used the main, xlab, and ylab arguments to display text on the plot, as shown:
> boxplot(x = boxplotFireShuSoldiersData, main = boxPlotFireShuSoldiersLabelMain, xlab = boxPlotFireShuSoldiersLabelX, ylab = boxPlotFireShuSoldiersLabelY)
Next, we created a multiple box plot that compared the number of Shu soldiers deployed by each battle method. The main, xlab, and ylab arguments remained from our single box plot, however our multiple box plot used the formula argument instead of x. Here, a formula allows us to break a dataset down into separate groups, thus yielding multiple boxes.
The basic format for a multiple box plot is as follows:
boxplot(formula = dataset ~ group)
In our case, we took our entire Shu soldier dataset (battleHistory$ShuSoldiers) and separated it by battle method (battleHistory$Method):
> boxplotAllMethodsShuSoldiersData <- battleHistory$ShuSoldiers ~ battleHistory$Method
Once incorporated into the boxplot(...) function, this formula resulted in a plot that contained four distinct boxes ambush, fire, head to head, and surround:
> boxplot(formula = boxplotAllMethodsShuSoldiersData, main = boxPlotAllMethodsShuSoldiersLabelMain, xlab = boxPlotAllMethodsShuSoldiersLabelX, ylab = boxPlotAllMethodsShuSoldiersLabelY)
- Which of the following best describes the result of the following code?
> boxplot(x = a)
a. A single box plot of the
adataset.b. A single box plot of the
xdataset.c. A multiple box plot of the
adataset that is grouped byx.d. A multiple box plot of the
xdataset that is grouped bya. - Which of the following best describes the result of the following code?.
> boxplot(formula = a ~ b)
a. A single box plot of the
adataset.b. A single box plot of the
bdataset.c. A multiple box plot of the
adataset that is grouped byb.d. A multiple box plot of the
bdataset that is grouped bya.