How to center stacked percent barchart labels - r

Question

I am trying to plot nice stacked percent barchart using ggplot2. I've read some material and almost manage to plot, what I want. Also, I enclose the material, it might be useful in one place:
How do I label a stacked bar chart in ggplot2 without creating a summary data frame?
Create stacked barplot where each stack is scaled to sum to 100%
R stacked percentage bar plot with percentage of binary factor and labels (with ggplot)
My problem is that I can't place labels where I want - in the middle of the bars.
You can see the problem in the picture above - labels looks awfull and also overlap each other.
What I am looking for right now is:
How to place labels in the midde of the bars (areas)
How to plot not all the labels, but for example which are greather than 10%?
How to solve overlaping problem?
For the Q 1. #MikeWise suggested possible solution. However, I still can't deal with this problem.
Also, I enclose reproducible example, how I've plotted this grahp.
library('plyr')
library('ggplot2')
library('scales')
set.seed(1992)
n=68
Category <- sample(c("Black", "Red", "Blue", "Cyna", "Purple"), n, replace = TRUE, prob = NULL)
Brand <- sample("Brand", n, replace = TRUE, prob = NULL)
Brand <- paste0(Brand, sample(1:5, n, replace = TRUE, prob = NULL))
USD <- abs(rnorm(n))*100
df <- data.frame(Category, Brand, USD)
# Calculate the percentages
df = ddply(df, .(Brand), transform, percent = USD/sum(USD) * 100)
# Format the labels and calculate their positions
df = ddply(df, .(Brand), transform, pos = (cumsum(USD) - 0.5 * USD))
#create nice labes
df$label = paste0(sprintf("%.0f", df$percent), "%")
ggplot(df, aes(x=reorder(Brand,USD,
function(x)+sum(x)), y=percent, fill=Category))+
geom_bar(position = "fill", stat='identity', width = .7)+
geom_text(aes(label=label, ymax=100, ymin=0), vjust=0, hjust=0,color = "white", position=position_fill())+
coord_flip()+
scale_y_continuous(labels = percent_format())+
ylab("")+
xlab("")

Answer 1

Here's how to center the labels and avoid plotting labels for small percentages. An additional issue in your data is that you have multiple bar sections for each colour. Instead, it seems to me all the bar sections of a given colour should be combined. The code below uses dplyr instead of plyr to set up the data for plotting:
library(dplyr)
# Initial data frame
df <- data.frame(Category, Brand, USD)
# Calculate percentages
df.summary = df %>% group_by(Brand, Category) %>%
summarise(USD = sum(USD)) %>% # Within each Brand, sum all values in each Category
mutate(percent = USD/sum(USD))
With ggplot2 version 2, it is no longer necessary to calculate the coordinates of the text labels to get them centered. Instead, you can use position=position_stack(vjust=0.5). For example:
ggplot(df.summary, aes(x=reorder(Brand, USD, sum), y=percent, fill=Category)) +
geom_bar(stat="identity", width = .7, colour="black", lwd=0.1) +
geom_text(aes(label=ifelse(percent >= 0.07, paste0(sprintf("%.0f", percent*100),"%"),"")),
position=position_stack(vjust=0.5), colour="white") +
coord_flip() +
scale_y_continuous(labels = percent_format()) +
labs(y="", x="")
With older versions, we need to calculate the position. (Same as above, but with an extra line defining pos):
# Calculate percentages and label positions
df.summary = df %>% group_by(Brand, Category) %>%
summarise(USD = sum(USD)) %>% # Within each Brand, sum all values in each Category
mutate(percent = USD/sum(USD),
pos = cumsum(percent) - 0.5*percent)
Then plot the data using an ifelse statement to determine whether a label is plotted or not. In this case, I've avoided plotting a label for percentages less than 7%.
ggplot(df.summary, aes(x=reorder(Brand,USD,function(x)+sum(x)), y=percent, fill=Category)) +
geom_bar(stat='identity', width = .7, colour="black", lwd=0.1) +
geom_text(aes(label=ifelse(percent >= 0.07, paste0(sprintf("%.0f", percent*100),"%"),""),
y=pos), colour="white") +
coord_flip() +
scale_y_continuous(labels = percent_format()) +
labs(y="", x="")

Answer 2

I followed the example and found the way how to put nice labels for simple stacked barchart. I think it might be usefull too.
df <- data.frame(Category, Brand, USD)
# Calculate percentages and label positions
df.summary = df %>% group_by(Brand, Category) %>%
summarise(USD = sum(USD)) %>% # Within each Brand, sum all values in each Category
mutate( pos = cumsum(USD)-0.5*USD)
ggplot(df.summary, aes(x=reorder(Brand,USD,function(x)+sum(x)), y=USD, fill=Category)) +
geom_bar(stat='identity', width = .7, colour="black", lwd=0.1) +
geom_text(aes(label=ifelse(USD>100,round(USD,0),""),
y=pos), colour="white") +
coord_flip()+
labs(y="", x="")