Bar charts

Introduction

Bar charts visualize counts of unique data point values in the sample space of a categorical variable.

Creating simulated data

cities <- sample(c("NYC", "Boston", "LA", "Seattle"),
                 100,
                 replace = TRUE)

table(cities)

## cities
##  Boston      LA     NYC Seattle 
##      24      26      31      19

as.numeric(table(cities))

## [1] 24 26 31 19

names(table(cities))

## [1] "Boston"  "LA"      "NYC"     "Seattle"

Simple bar chart

p1 <- plot_ly(x = names(table(cities)),
              y = as.numeric(table(cities)),
              name = "Cities",
              type = "bar")
p1

Adding a title and axes names

p2 <- plot_ly(x = names(table(cities)),
              y = as.numeric(table(cities)),
              name = "Cities",
              type = "bar") %>% 
  layout(title = "Number of offices in each city",
         xaxis = list(title = "Cities",
                      zeroline = FALSE),
         yaxis = list(title = "Number",
                      zeroline = FALSE))
p2

Creating simulated data for a data.frame

df <- data.frame(Cities = cities,
                 Group = sample(c("A", "B"),
                 100,
                 replace = TRUE))
head(df)

##    Cities Group
## 1     NYC     A
## 2      LA     B
## 3      LA     A
## 4      LA     A
## 5 Seattle     A
## 6      LA     A

Greate two new data.frame object for groups A and B.

groupA <- df %>% filter(Group == "A")
groupB <- df %>% filter(Group == "B")

table(groupA$Cities)

## 
##  Boston      LA     NYC Seattle 
##      11      14      14       9

names(table(groupA$Cities))

## [1] "Boston"  "LA"      "NYC"     "Seattle"

as.numeric(table(groupA$Cities))

## [1] 11 14 14  9

gBarChart <- data.frame(Cities = names(table(groupA$Cities)),
                      GroupA = as.numeric(table(groupA$Cities)),
                      GroupB = as.numeric(table(groupB$Cities)))
head(gBarChart)

##    Cities GroupA GroupB
## 1  Boston     11     13
## 2      LA     14     12
## 3     NYC     14     17
## 4 Seattle      9     10

Grouped bar chart

p3 <- plot_ly(gBarChart,
              x = ~Cities,
              y = ~GroupA,
              type = "bar",
              name = "Group A") %>% 
  add_trace(y = ~GroupB,
            name = "Group B") %>% 
  layout(yaxis = list(title = "Cities"),
         barmode = "group")
p3

Stacked bar chart

p4 <- plot_ly(gBarChart,
              x = ~Cities,
              y = ~GroupA,
              type = "bar",
              name = "group A") %>% 
  add_trace(y = ~GroupB,
            name = "Group B") %>% 
  layout(yaxis = list(title = "Cities"),
         barmode = "stack")
p4

Changing the color

p5 <- plot_ly(x = names(table(cities)),
              y = as.numeric(table(cities)),
              name = "Cities",
              type = "bar",
              marker = list(color = "rgba(255, 70, 0, 0.7)",
                            line = list(color = "rgba(0, 0, 0, 0.5)",
                                        width = 1.5))) %>% 
  layout(title = "Number of offices per city",
         xaxis = list(title = "Cities",
                      zeroline = FALSE),
         yaxis = list(title = "Number",
                      zeroline = FALSE))
p5

p6 <- plot_ly(x = names(table(cities)),
              y = as.numeric(table(cities)),
              name = "Cities",
              type = "bar",
              marker = list(color = "rgba(255, 70, 0, 0.7)",
                            line = list(color = "rgba(0, 0, 0, 0.5)",
                                        width = 1.5))) %>% 
  layout(title = "Number of offices per city",
         xaxis = list(title = "Cities",
                      zeroline = FALSE,
                      tickangle = -20),
         yaxis = list(title = "Number",
                      zeroline = FALSE))
p6

Specifying the color of each bar

Color can be specified of each bar.

p7 <- plot_ly(x = names(table(cities)),
              y = as.numeric(table(cities)),
              name = "Cities",
              type = "bar",
              marker = list(color = c("rgba(150, 150, 150, 0.7)",
                                      "rgba(150, 150, 150, 0.7",
                                      "rgba(255, 20, 0, 0.7)",
                                      "rgba(150, 150, 150, 0.7"))) %>% 
  layout(title = "Number of offices per city",
         xaxis = list(title = "Cities",
                      zeroline = FALSE),
         yaxis = list(title = "Number",
                      zeroline = FALSE))
p7