Grouped barplot with ggplot2: grouping two numeric variables under each year

Question

My problem is simple but I have not been able to find a post that solves it.

Here is my data set DF:

   Year     CO2Seq       CO2Seq2
1  2000     1135704      1107400
2  2003     3407111      3444508
3  2010     1703555      1661100
4  2015     2271407      2296339

I would like to create a barplot where the bars CO2Seq and CO2Seq2 are next to each other for each year.

For the moment, I have only been able to create a simple barplot for CO2Seq with this script

ggplot(DF,aes(x=factor(Year), y=CO2Seq))+geom_bar(stat="identity")

Could you help me?

Thanks a lot

iroha · Accepted Answer · 2019-09-26 11:35:00Z

1

ggplot has generally been designed for use with long rather than wide data, so the first step is to reshape your data, then plotting is straightforward.

library(ggplot2)
library(tidyr)

df %>%
  pivot_longer(col = -Year) %>%
  ggplot(aes(x = factor(Year), y = value, fill = name)) +
  geom_bar(stat = "identity", position = "dodge")

answered Sep 26, 2019 at 11:35

iroha

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3 Comments

Xav64 Over a year ago

Thanks, this looks great but I don't understand what you mean by long rather than wide. I should have mentionned that my real dataset has hundreds of rows. Would it still be important to reshape it?

iroha Over a year ago

Yes, it will still need to be reshaped. Compare the difference between your example df (which is wide) and df %>% pivot_longer(col = -Year) (which is long).

Xav64 Over a year ago

Aaaah ok now I get what you mean. This operation allows us to only have one numeric column and makes the grouping easier! Thanks a lot H1!

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