How to reorder bar charts with ggplot2

Problem

We'd like to reorder the bars of a bar chart. In our example below, the bars are not plotted in ascending or descending order.

library(tidyverse)
ggplot(df, aes(x = Position)) + geom_bar()

Data frame

df <- structure(list(Position = structure(c(3L, 3L, 1L, 1L, 1L, 2L), .Label = c("Defense", 
"Striker", "Zoalkeeper"), class = "factor"), Name = structure(c(2L, 
1L, 3L, 5L, 4L, 6L), .Label = c("Frank", "James", "Jean", "John", 
"Steve", "Tim"), class = "factor")), class = "data.frame", row.names = c(NA, 
-6L))

    Position  Name
1 Zoalkeeper James
2 Zoalkeeper Frank
3    Defense  Jean
4    Defense Steve
5    Defense  John
6    Striker   Tim

Solution

An alternative is using reorder to order the levels of a factor. In ascending (n) or descending order (-n) based on the count:

• Descending order

df %>%
  count(Position) %>%
  ggplot(aes(x = reorder(Position, -n), y = n)) +
  geom_bar(stat = 'identity') +
  xlab("Position")


• Ascending order

df %>%
  count(Position) %>%
  ggplot(aes(x = reorder(Position, n), y = n)) +
  geom_bar(stat = 'identity') +
  xlab("Position")

References

• stackoverflow

How to subset a contingency table in R?

Problem

We'd like to subset a contingency table. In our example, we use the dataset chickwts, subsetting those types of feed for which we have more than 11 observations.

table(chickwts$feed)

   casein horsebean   linseed  meatmeal   soybean sunflower 
       12        10        12        11        14        12

Solution

• Base package

Using the function subset.

subset(data.frame(table(chickwts$feed)), Freq > 11)

• dplyr

library(dplyr)
chickwts %>% 
  count(feed) %>%
  filter(n > 11) 

Results

 # base
      Var1 Freq
1    casein   12
3   linseed   12
5   soybean   14
6 sunflower   12

# dplyr

# A tibble: 4 × 2
       feed     n
      
1    casein    12
2   linseed    12
3   soybean    14
4 sunflower    12

References

• stackoverflow

Conditional formatting to hide cell content in Excel

Problem

We would like to hide the contents of a cell based on the value of another cell.

Solution

In A2 we apply a conditional formatting rule that hides the content of that cell if it is equal to B2.

In Conditional Formatting we create the following rule: =$A$2=$B$2, then press Format...

1. On the Format menu, click Cells, and then click the Number tab.
2. Under Category, click Custom.
3. In the Type box, type ;;; (that is, three semicolons in a row), and then click OK

Notes

Why do we need to add three semicolons as a custom Excel format? The reason behind is that custom number formats consist of four sections separated by three semicolons, so if we just type three semicolons and nothing else, the cell will appear empty.

References

• stackoverflow

How to add a text box to a plot in R

Problem

We want to add a text box to a plot in R. First, we will use a very convoluted code to get it done.

# A plot
plot(x = runif(1000), y = runif(1000), type = "p", pch = 16, col = "#40404050")

# Text box parameters
myText <- "some Text"
posCoordsVec <- c(0.5, 0.5)
cex <- 2

# Rectangle
textHeight <- graphics::strheight(myText, cex = cex)
textWidth <- graphics::strwidth(myText, cex = cex)
pad <- textHeight*0.3
rect(xleft = posCoordsVec[1] - textWidth/2 - pad, 
        ybottom = posCoordsVec[2] - textHeight/2 - pad, 
        xright = posCoordsVec[1] + textWidth/2 + pad, 
        ytop = posCoordsVec[2] + textHeight/2 + pad,
        col = "lightblue", border = NA)

# Text coordinates
text(posCoordsVec[1], posCoordsVec[2], myText, cex = cex)

Solution

• Base graphics

We use the function legend, same colour for the box line (box.col) and the background (bg), adjusting the text inside with the argument adj.

plot(x = runif(1000), y = runif(1000), type = "p", pch = 16, col = "#40404050")
legend(0.4, 0.5, "Some text", box.col = "lightblue", bg = "lightblue", adj = 0.2)


• ggpplot2

With ggplot2 we need the function geom_label. The text will be automatically aligned inside the box, we remove the borders with label.size = NA.

library(ggplot2)
df <- data.frame(x = runif(1000), y = runif(1000))
ggplot(data = df, aes(x = x , y = y))+ 
  geom_point(alpha = 0.2)+
  geom_label(aes(x = 0.5, y = 0.5, label = "Some text"), 
             fill = "lightblue", label.size = NA, size = 5)

References

• stackoverflow
• legend
• geom_label