# ggplot2

### Simple bar plot

Suppose you have those data in df:

year n
2017 381
2018 315

You want to plot how many n are in each year in a simple bar plot.

plot <- ggplot(df, aes(x = year, y = n)) +
geom_bar(stat = "identity")
plot


Do NOT forget to add stat = "identity" in geom_bar(). It tells ggplot2 to “count” n.

Fig. 1: Here's the result of the aforementioned code. Of course you can customize its look if you are not happy with the colours, and so on.

### Percentage bar plot

plot <- ggplot(df, aes(x = var1, y = (..count..)/sum(..count..))) +
geom_bar()
plot


More sophisticated code, not tested yet:

ggplot(df, aes(x= var1,  group=var_group)) +
geom_bar(aes(y = ..prop.., fill = factor(..x..)), stat="count") +
geom_text(aes( label = scales::percent(..prop..),
y= ..prop.. ), stat= "count", vjust = -.5) +
labs(y = "Percent", fill="var1") +
facet_grid(~var_group) +
scale_y_continuous(labels = scales::percent)


Requires the library scales.

(Same source)

### Plot several series in one single bar plot

ggplot(df, aes(x=var1, y=(..count..), fill=var2)) +
geom_bar(stat="identity", position="dodge")


If the variable used with fill is kind of categorical (for instance it's years), beware to be sure it's a factor (as.factor(var2)). Otherwise it may be treated as a continuous variable, and displayed incorrectly.

(..count..) means that ggplot2 will display the count of var1 for each value of var2.

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