How to avoid overlap between segments while plotting a Gantt chart with ggplot in R

Question

Dears, I have a question regarding plotting a Gantt chart with ggplot in R. Whenever I plot my data there is an overlap between segments. For example (as per the attached plot), you will see that product A1 should have four segments (as per the data attached) but due to the overlap you can see that there are only two segments (as per the attached image link). I would like to plot every segment for the same product in a separate row to avoid such overlapping. Once I have each segment on a row, I would like to have the product name for the group of segments is shown only one time. I am attaching the code I used in addition to the plot.

Thanks in advance Mohamed

Product Codes   Batch Number    Start   End
A                  1            1000    1500
A                  1            1400    2000
A                  1            1800    2300
A                  1            6573    6905
A                  2            13773   14105
A                  2            5040    5372
A                  2            720     1052
A                  3            1921    2253
A                  3            3933    4265
A                  3            13441   13773

library(ggplot2)
library(grid)
library(dplyr)
library(gtable)
library(readxl)
library(readxl)
library(reshape2)
library(ggrepel)
library(RColorBrewer)

Book2 <- read_excel("C:/Users/...stack.xlsx", sheet = "Sheet1")
attach(Book2)
df2<-Book2

actcols <- c("#d95f0e","#756bb1","#0218a2","#ffb703", "#f76f73", "#027fdc", "#07c4c5","#303030","#11793b","#5d7261","#3f5f34","#905435","#997940","#ab3434","#961B4D")
myColors <- brewer.pal(5,"Set1")

start<-as.POSIXct('04/06/2020',format='%m/%d/%Y') 

date<-(df2$Start)*60+start
zz2<-(df2$End)*60+start

Product<-paste(df2$`Product Codes`,df2$`Batch Number`)

plot2 <-  ggplot(df2, aes(x=date,xend=zz2-900,y=Product, yend=Product,color=Product))+ geom_segment(stat = "identity")+ theme_bw()+ geom_segment(size=5)+ 
  theme(plot.title=element_text(size=24, face="bold"), 
        axis.text.x=element_text(size=10), 
        axis.text.y=element_text(size=14),
        axis.title.x=element_text(size=16),
        axis.title.y=element_text(size=14),
        legend.title = element_text(size=16),
        legend.position="top")+scale_x_datetime(date_labels ="%a %b %d",  date_breaks  ="1 day") +
  theme(axis.text.x = element_text(hjust=2.5))
plot2

Answer 1

Try this. Basic Idea is to add the segment numbers to your Product variable and map the new Product_segment variable on y:

library(RColorBrewer)
library(ggplot2)
library(dplyr)

df2 <- read.table(text = "'Product Codes'   'Batch Number'    Start   End
A                  1            1000    1500
A                  1            1400    2000
A                  1            1800    2300
A                  1            6573    6905
A                  2            13773   14105
A                  2            5040    5372
A                  2            720     1052
A                  3            1921    2253
A                  3            3933    4265
A                  3            13441   13773", header = TRUE, stringsAsFactors = FALSE)

df2 <- df2 %>% 
  rename(`Product Codes` = Product.Codes, `Batch Number` = Batch.Number)

actcols <- c("#d95f0e","#756bb1","#0218a2","#ffb703", "#f76f73", "#027fdc", "#07c4c5","#303030","#11793b","#5d7261","#3f5f34","#905435","#997940","#ab3434","#961B4D")
myColors <- brewer.pal(5,"Set1")

start<-as.POSIXct('04/06/2020',format='%m/%d/%Y') 

# Data wrangling
df3 <- df2 %>%
  mutate(
    date = Start * 60 + start,
    zz2 = End * 60 + start  - 900,
    Product = paste(`Product Codes`, `Batch Number`)
  ) %>% 
  select(-Start, -End) %>% 
  # Add segment number
  group_by(Product) %>% 
  arrange(Product, date) %>% 
  mutate(segment = 1,
         segment = cumsum(segment),
         Product_segment = paste(Product, segment),
         y.labels = ifelse(segment == n_distinct(segment), Product, "")) %>% 
  ungroup() 

y.labels <- df3$y.labels

plot2 <-  ggplot(df3, aes(x = date, xend = zz2, y = Product_segment, yend = Product_segment, color = Product)) + 
  geom_segment(size = 10) + 
  scale_x_datetime(date_labels ="%a %b %d",  date_breaks  ="1 day") +
  scale_y_discrete(labels = y.labels) +
  labs(x = NULL, y = NULL) +
  theme_bw() + 
  theme(plot.title=element_text(size=24, face="bold"), 
        axis.text.x=element_text(size=10), 
        axis.text.y=element_text(size=14),
        axis.title.x=element_text(size=16),
        axis.title.y=element_text(size=14),
        legend.title = element_text(size=16),
        legend.position="top")
plot2

Edit: Subplots

subplot2 <-  ggplot(df3, aes(x = date, xend = zz2, y = factor(segment), yend = factor(segment), color = Product)) + 
  geom_segment(size = 9) + 
  scale_x_datetime(date_labels ="%a %b %d",  date_breaks  ="1 day") +
  labs(x = NULL, y = NULL) +
  facet_wrap(~ Product, ncol = 1, scales = "free_y") +
  theme_bw() + 
  theme(plot.title=element_text(size=24, face="bold"), 
        axis.text.x=element_text(size=10), 
        axis.text.y=element_text(size=14),
        axis.title.x=element_text(size=16),
        axis.title.y=element_text(size=14),
        legend.title = element_text(size=16),
        legend.position="top")
subplot2

^{Created on 2020-04-08 by the reprex package (v0.3.0)}