Construct Bar Graphs
First, let’s create the frequency and relative frequency distributions from the body part data in Table 1.
library(mosaic)
Table1 <- read.csv("https://sullystats.github.io/Statistics6e/Data/Chapter2/Table1.csv")
Table1_Freq <- data.frame(tally(~Location,data=Table1))
Table1_RelFreq <- data.frame(tally(~Location,data=Table1,format="prop"))Bar Graphs from Summarized Data
Using the summarized data from the frequency table, we can create a bar graph of the frequencies.
To create a frequency bar graph, use the following syntax:
barplot(Frequency_table$Freq,names.arg = Frequency_table$qualitative_variable_name,las=2)- Frequency_table is the name of the data frame containing the summarized data.
- Freq is the name of column containing the frequencies.
- las = 2 is only necessary if you want to rotate the x-axis labels.
- names.arg= is used to declare the x-axis labels on the bar graph.
When using basic plot functions in R, the following inputs are very valuable and consistent across all plot functions:
- Within a plot function, use main = “Main Title” to give your graph a title.
- Within a plot function, use xlab = “X-Axis Title” to give your x-axis a title.
- Within a plot function, use ylab = “Y-Axis Title” to give your y-axis a title.
- Within a plot function, use col = “color” to give your graph a color other than gray. In this input, you can type a generic color like “blue” or you can search online at www.color-hex.com for Hex color codes like “#6897bb”.
In the following barplot command, these inputs are used to make the bar graph more visually appealing and straight-forward.
barplot(Table1_Freq$Freq,names.arg=Table1_Freq$Location,main="Types of Rehabilitation",xlab="Body Part",ylab="Frequency",col='#6897bb',las=2)
To create a relative frequency bar graph from the summarized data, use the same command except use the saved relative frequency distribution.
barplot(Table1_RelFreq$Freq,names.arg=Table1_RelFreq$Location,main="Types of Rehabilitation",xlab="Body Part",ylab="Relative Frequency",col='#6897bb',las=2)
Bar Graphs from Raw Data
Using Base r
Table1 <- read.csv("https://sullystats.github.io/Statistics6e/Data/Chapter2/Table1.csv")First, we draw a frequency bar graph.
bargraph(~Location,data=Table1,main="Types of Rehabilitation",ylab="Frequency",xlab="Body Part",col='#3832a8')
Now, draw a relative frequency bar graph.
bargraph(~Location,data=Table1,main="Types of Rehabilitation",ylab="Relative Frequency",xlab="Body Part",col='#3832a8',type="proportion")