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A bar chart, also known as a bar graph, is a statistical chart that uses the length of rectangles as a variable. Bar charts can be horizontal or vertical, and each rectangle can have a different color. The R language uses the `barplot()` function to create bar charts, with the following format: ```r barplot(H, xlab, ylab, main, names.arg, col, beside) Parameter Description: * **H**: A vector or matrix containing the numerical values for the chart. Each value represents the height of a rectangular bar. * **xlab**: Label for the x-axis. * **ylab**: Label for the y-axis. * **main**: Title of the chart. * **names.arg**: Names for each rectangular bar. * **col**: Colors for each rectangular bar. Next, we create a simple bar chart: ## Example ```r # Prepare a vector cvd19 = c(83534, 2640626, 585493) # Display the bar chart barplot(cvd19) When you run the plotting program, it will generate a PDF file (Rplots.pdf) in the current directory. Opening the file will show the graphical effect as follows: !(#) To better convey information, we can add a title, colors, and names for each rectangular bar to the chart. Below, we create a statistical chart of confirmed COVID-19 cases in China, the United States, and India as of July 1, 2020. For Chinese fonts, you need to set the font parameter `family='GB1'`: ## Example ```r cvd19 = c(83534, 2640626, 585493) barplot(cvd19, main = "COVID-19 Bar Chart", col = c("#ED1C24", "#22B14C", "#FFC90E"), names.arg = c("China", "USA", "India"), family = 'GB1' ) !(#) The data in `barplot` can be either a vector or a matrix. Now, let's generate a comparison chart of COVID-19 cases for June and July. First, prepare the data: | | China | USA | India | |-------|-------|----------|--------| | June | 83017 | 1794546 | 190535 | | July | 83534 | 2640626 | 585493 | Convert it into a matrix and generate a bar chart in a side-by-side format, also displaying a color legend. Here, we set our own font library. For details, please refer to (#). ## Example ```r library(showtext); font_add("SyHei", "SourceHanSansSC-Bold.otf"); cvd19 = matrix( c(83017, 83534, 1794546, 2640626, 190535, 585493), 2, 3 ) # Set the filename, output as png png(file = "-bar-1.png") # Load the font showtext_begin(); colnames(cvd19) = c("China", "USA", "India") rownames(cvd19) = c("June", "July") barplot(cvd19, main = "COVID-19 Bar Chart", beside = TRUE, legend = TRUE, family = 'SyHei') # Unload the font showtext_end(); The following code will generate a `-bar-1.png` file in the current program directory, as shown below: !(#) The color legend we set will be the color sample for each group: ## Example ```r library(plotrix) library(showtext); font_add("SyHei", "SourceHanSansSC-Bold.otf"); cvd19 = matrix( c(83017, 83534, 1794546, 2640626, 190535, 585493), 2, 3 ) # Set the filename, output as png png(file = "-bar-2.png") # Load the font showtext_begin(); colnames(cvd19) = c("China", "USA", "India") rownames(cvd19) = c("June", "July") barplot(cvd19, main = "COVID-19 Bar Chart", beside = TRUE, legend = TRUE, col = c("blue", "green"), family = 'SyHei') # Unload the font showtext_end(); The following code will generate a `-bar-2.png` file in the current program directory, as shown below: !(#) ### The `beside` Parameter The `beside` parameter sets the stacking method of the rectangular bars. The default is `FALSE`: * When **`beside=FALSE`**, the height of the bar chart is the value of the matrix, and the rectangular bars are stacked horizontally. * When **`beside=TRUE`**, the height of the bar chart is the value of the matrix, and the rectangular bars are placed side-by-side. ## Example ```r library(showtext); font_add("SyHei", "SourceHanSansSC-Bold.otf"); cvd19 = matrix( c(83017, 83534, 1794546, 2640626, 190535, 585493), 2, 3 ) # Set the filename, output as png png(file = "-bar-3.png") # Load the font showtext_begin(); colnames(cvd19) = c("China", "USA", "India") rownames(cvd19) = c("June", "July") barplot(cvd19, main = "COVID-19 Bar Chart", beside = FALSE, legend = TRUE, col = c("blue", "green"), family = 'SyHei') # Unload the font showtext_end(); The following code will generate a `-bar-3.png` file in the current program directory, as shown below: !(#)