ggplot - bar plot for two variable from the same data frame

Question

I need to generate a plot with bar graph for two variables.

I can create a column graph for one variable like below

df <- head(mtcars)
df$car <- row.names(df)
ggplot(df) + geom_col(aes(x=car, y=disp))

how to go about getting a chart like below ( created in excel) - essentially I need add bar plot of more than one variable.

@Linus - thanks. I will refer to that part for the secondary axis question. — user3206440
– user3206440, Commented Dec 21, 2017 at 15:09

Gregor Thomas · Accepted Answer · 2017-12-21 15:16:55Z

2

With ggplot you need to convert data to long format so that one column defines the color and one column defines the y value:

library(tidyr)
df$car = row.names(df)
df_long = gather(df, key = var, value = value, disp, hp)
ggplot(df_long, aes(x = car, y = value, fill = var)) +
  geom_bar(stat = 'identity', position = 'dodge')

answered Dec 21, 2017 at 15:16

Gregor Thomas

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4 Comments

user3206440 Over a year ago

how can we bring the legend to the top centered horizontally and set the y-axis label to the variable names !!

Gregor Thomas Over a year ago

I'm sure if you search the [ggplot2] tag for those questions you can find excellent solutions!

user3206440 Over a year ago

just an unrelated comment - I see that you are using = rather than <-. Is this generally accepted practice ?

Gregor Thomas Over a year ago

It's uncommon, but it's just fine. I prefer it so I do it.

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