如何用R的barplot()函数从原始CSV数据创建分组条形图

Got it, let's walk through how to make that grouped bar chart in R step by step. Here's exactly what you need to do:

Step 1: Format your data into a proper CSV file #

First, save your data as a CSV with a clear column for the group labels. Create a file named scores.csv with this content:

Group,CT,VT,TT
A*,5.923076923,6.529411765,5.305555556
Not A*,5.555555556,6.434782609,5.352941176

Make sure this file is saved in your R working directory (you can check your current working directory with getwd()).

Step 2: Install and load required packages #

We'll use the tidyverse package, which includes ggplot2 for plotting and tidyr to reshape your data. Run these lines (only install once if you don't have the package yet):

# Install the package (run once)
install.packages("tidyverse")

# Load the package every time you start R
library(tidyverse)

Step 3: Read the CSV into R #

Import your data into an R data frame:

data <- read.csv("scores.csv", stringsAsFactors = FALSE)

Step 4: Reshape the data to long format #

Grouped bar charts in ggplot2 work best with "long" formatted data (where each row represents a single observation). We'll convert your wide data to long using pivot_longer:

long_data <- data %>%
  pivot_longer(cols = -Group, names_to = "Metric", values_to = "Score")

This converts your CT/VT/TT columns into rows under a new Metric column, paired with their corresponding scores in the Score column.

Step 5: Create the grouped bar chart #

Now use ggplot2 to build your chart:

ggplot(long_data, aes(x = Metric, y = Score, fill = Group)) +
  # Create grouped bars (position_dodge ensures they're side-by-side)
  geom_col(position = position_dodge(width = 0.8), width = 0.7) +
  # Add labels and title
  labs(
    title = "Scores by Metric and Group",
    x = "Metric",
    y = "Score",
    fill = "Group"
  ) +
  # Use a clean theme
  theme_minimal() +
  # Center the plot title
  theme(plot.title = element_text(hjust = 0.5))

If you want to customize the colors of the bars, add this line to the plot code:

scale_fill_manual(values = c("A*" = "#2c3e50", "Not A*" = "#7f8c8d"))

Just replace the hex codes with any colors you prefer.

内容的提问来源于stack exchange，提问作者spar31415