Combine Two ggplot2 Plots from Different Data Frames in R (Example)

In this article you’ll learn how to draw a ggplot2 plot based on several different data sources in the R programming language.

Table of contents:

1) Example Data, Add-On Packages & Default Plot

2) Example: Drawing ggplot2 Plot Based on Two Different Data Frames

3) Video, Further Resources & Summary

Let’s do this…

Example Data, Add-On Packages & Default Plot

Consider the following example data:

data1 <- data.frame(x = 1:5,        # Create first data frame
                    y = 1:5)
data1                               # Print first data frame
#   x y
# 1 1 1
# 2 2 2
# 3 3 3
# 4 4 4
# 5 5 5
data2 <- data.frame(x = 2:6,        # Create second data frame
                    y = 8:4)
data2                               # Print second data frame
#   x y
# 1 2 8
# 2 3 7
# 3 4 6
# 4 5 5
# 5 6 4

The previous RStudio console output shows the structure of our example data sets – Both data frames contains two numeric columns with the variable names x and y.

If we want to use the functions of the ggplot2 package, we also have to install and load ggplot2:

install.packages("ggplot2")         # Install ggplot2 package
library("ggplot2")                  # Load ggplot2 package

Now, we can move on to the example…

Example: Drawing ggplot2 Plot Based on Two Different Data Frames

This section shows how to use the ggplot2 package to draw a plot based on two different data sets.

For this, we have to set the data argument within the ggplot function to NULL. Then, we are specifying two geoms (i.e. geom_point and geom_line) and define the data set we want to use within each of those geoms.

ggp <- ggplot(NULL, aes(x, y)) +    # Draw ggplot2 plot based on two data frames
  geom_point(data = data1, col = "red") +
  geom_line(data = data2, col = "blue")
ggp                                 # Draw plot

r graph figure 1 combine two ggplot2 plots from different data frames r

Figure 1 visualizes the output of the previous R code – A ggplot2 graph created based on multiple different data matrices.

Video, Further Resources & Summary

If you need more information on the R programming codes of this article, you may watch the following video of my YouTube channel. In the video, I illustrate the content of this article.

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Furthermore, I can recommend having a look at some of the other tutorials of this homepage:

Summary: In this article, I explained how to create a ggplot2 graph with two different data sets in the R programming language – a very nice method in case you want to add a new layer or series of data points to a ggplot2 plot. Let me know in the comments section, in case you have additional questions.

6 Comments. Leave new

Mauricio
January 14, 2021 3:21 pm

Hi, how are you?
I need your help!
I have 2 data frame with 3 columns each one (with 264.000 rows). The columns “Id1” (first) and “Id2” (second) are the same in both files (.tsv).
I tried to merge the columns Id1 and Id2 for two files but this result in an error: cannot allocate vector of size 972.2 Mb in R.
I wanna plot (scatter plot) the numerical values in the third columns for the two different files: Val1 (third column for file 1) VS Val_1 (third column for file 2).
Can you help me please?

Reply
- Joachim
  January 15, 2021 7:12 am
  
  Hey Mauricio,
  
  This sounds like a huge file! Do you really need all these data points or is it possible to make the file smaller before merging it?
  
  You may have a look at this tutorial: https://statisticsglobe.com/r-error-cannot-allocate-vector-of-size-n-gb It gives some tips on how to handle the error message you are facing.
  
  I hope that helps!
  
  Joachim
  
  Reply
Sudipta Roy
March 2, 2021 1:23 pm

Hello,
I have a problem. I am working on two NetCDF files and I plotted them separately without having any problems. When I was combining them in one by following your method, “Error in FUN(X[[i]], …) : object ‘x’ not found” – this error keeps coming. What should I do? I want to plot from multiple NetCDF files in a single plot. Not to mention, spatial references, units and resolutions are same in the every files.

Reply
- Joachim
  March 2, 2021 2:17 pm
  
  Hi Sudipta,
  
  Could you post your R code? It’s difficult to tell the problem without seeing it.
  
  Thanks
  
  Joachim
  
  Reply
Sael
March 24, 2021 2:15 am

Your past saved me!
Could you explain how to add the legend to the figure?
I tried to add the legend but I could not do it.
Thanks

Reply
- Joachim
  March 24, 2021 6:41 am
  Hi Sael,
  
  Thanks a lot, glad the tutorial helped!
  
  One solution would be to add the aes() function to both geoms, i.e.
  geom_point(data = data1, aes(col = "red")) + geom_line(data = data2, aes(col = "blue"))
  geom_point(data = data1, aes(col = "red")) + geom_line(data = data2, aes(col = "blue"))
  Note that this changes the colors to the default color palette of the ggplot2 package.
  
  Regards
  
  Joachim
  Reply