R visualization: barplot by ggplot2

barplot with point

Introduction

Barplot with jitter shows the mean and standard deviation or standard error between groups.

Loading required packages

knitr::opts_chunk$set(message = FALSE, warning = FALSE)

library(tidyverse)
library(ggpubr)

rm(list = ls())
options(stringsAsFactors = F)

# group & color
dose_names <- c("0.5", "1", "2")
dose_colors <- c("#0073C2FF", "#EFC000FF", "#CD534CFF")

supp_names <- c("OJ", "VC")
supp_colors <- c('#999999','#E69F00')

Data preparation

  • Loading ToothGrowth dataset

  • Factorizing categorical variables

data("ToothGrowth")

plotdata <- ToothGrowth |>
  dplyr::mutate(dose = factor(as.character(dose), levels = dose_names),
                supp = factor(supp, levels = supp_names)) |>
  dplyr::rename(Group = dose,
                Subgroup = supp,
                Index = len) |>
  dplyr::select(Group, Subgroup, Index)

head(plotdata)
##   Group Subgroup Index
## 1   0.5       VC   4.2
## 2   0.5       VC  11.5
## 3   0.5       VC   7.3
## 4   0.5       VC   5.8
## 5   0.5       VC   6.4
## 6   0.5       VC  10.0
  • Calculating mean & sd & se
data_summary <- function(data, varname, groupnames){

  require(plyr)

  summary_func <- function(x, col) {
    mean_value <- mean(x[[col]], na.rm = TRUE)
    sd_value <- sd(x[[col]], na.rm = TRUE)
    length_n <- length(x[[col]])

    # standard error= standard deviation/squareroot(n)
    se_value <- sd_value / sqrt(length_n)

    return(c(mean = mean_value, sd = sd_value, se = se_value))
  }

  data_sum <- ddply(data, groupnames, .fun=summary_func, varname)
  data_sum <- rename(data_sum, c("mean" = varname))

  return(data_sum)
}

dat_cal_one <- data_summary(
  plotdata,
  varname = "Index",
  groupnames = "Group")

head(dat_cal_one)
##   Group  Index       sd        se
## 1   0.5 10.605 4.499763 1.0061776
## 2     1 19.735 4.415436 0.9873216
## 3     2 26.100 3.774150 0.8439257
dat_cal_two <- data_summary(
  plotdata,
  varname = "Index",
  groupnames = c("Group", "Subgroup"))

head(dat_cal_two)
##   Group Subgroup Index       sd        se
## 1   0.5       OJ 13.23 4.459709 1.4102837
## 2   0.5       VC  7.98 2.746634 0.8685620
## 3     1       OJ 22.70 3.910953 1.2367520
## 4     1       VC 16.77 2.515309 0.7954104
## 5     2       OJ 26.06 2.655058 0.8396031
## 6     2       VC 26.14 4.797731 1.5171757

barplot with single group

  • create bar by geom_bar

  • add point by geom_jitter

pl <- ggplot(data = dat_cal_one, aes(x = Group, y = Index, fill = Group, color = Group)) +
  geom_bar(stat = "identity", color = "white", position = position_dodge()) +
  geom_errorbar(aes(ymin = Index, ymax = Index + sd),
                width = 0.2, position = position_dodge(width = 0.9),
                linewidth = 1) +
  stat_compare_means(data = plotdata,
                     aes(x = Group, y = Index),
                     comparisons = list(c("0.5", "1"),
                                        c("1", "2")),
                     label = "p.signif") +
  geom_jitter(data = plotdata,
             aes(x = Group, y = Index),
             size = 2, color = "gray10", show.legend = FALSE, pch = 21) +
  labs(x = "") +
  scale_y_continuous(expand = expansion(mult = c(0, 0.1))) +
  scale_fill_manual(values = dose_colors) +
  scale_color_manual(values = dose_colors) +
  guides(color = "none", fill = "none") +
  theme_classic() +
  theme(axis.title = element_text(size = 12, color = "black", face = "bold"),
        axis.text = element_text(size = 10, color = "black"),
        text = element_text(size = 9, color = "black"))

pl

barplot with two groups

  • create bar by geom_bar

  • add point by geom_jitter

pl2 <- ggplot(data = dat_cal_two, aes(x = Group, y = Index, fill = Subgroup, color = Subgroup)) +
  geom_bar(stat = "identity", color = "white", position = position_dodge()) +
  geom_errorbar(aes(ymin = Index - sd, ymax = Index + sd),
                width = 0.2, position = position_dodge(width = 0.9),
                size = 1) +
  stat_compare_means(data = plotdata,
                     aes(x = Group, y = Index, group = Subgroup),
                     label = "p.signif",
                     label.y = c(21, 28, 36)) +
  geom_point(data = plotdata,
             aes(x = Group, y = Index, shape = Subgroup),
                 position = position_jitterdodge(jitter.width = 0.5,
                                                 dodge.width = 0.7),
             size = 2, color = "gray50", show.legend = FALSE) +
  labs(x = "") +
  scale_y_continuous(expand = expansion(mult = c(0, 0.1))) +
  scale_fill_manual(values = supp_colors) +
  scale_color_manual(values = supp_colors) +
  scale_shape_manual(values = c(1, 21)) +
  guides(color = "none", shape = "none") +
  theme_classic() +
  theme(axis.title = element_text(size = 12, color = "black", face = "bold"),
        axis.text = element_text(size = 10, color = "black"),
        text = element_text(size = 9, color = "black"))

pl2

Conclusion

Compared to single boxplot, barplot focus on the mean and variation of data per group.

Systemic information

devtools::session_info()
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Reference

Hua Zou
Hua Zou
Senior Bioinformatic Analyst

My research interests include host-microbiota intersection, machine learning and multi-omics data integration.