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

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

Letâ€™s do thisâ€¦

## 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 â€“ 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

Now, we can move on to the exampleâ€¦

## 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```

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

## Video, Further Resources & Summary

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 â€“ 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.

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• Hi, how are you?
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).

• 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.

• Hi Sudipta,

Could you post your R code? It’s difficult to tell the problem without seeing it.

Thanks

Joachim

Could you explain how to add the legend to the figure?
I tried to add the legend but I could not do it.
Thanks

• 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"))```

Note that this changes the colors to the default color palette of the ggplot2 package.

Regards

Joachim

• I got blow error:
Error: Aesthetics must be either length 1 or the same as the data (5): y

I have used data1 having 5 rows and data2 having 8 rows, how to solve this issue. How can I plot data from two different files having different number of rows.

• Hey Ramki,

Iâ€™m sorry for the late response, I just came back from holidays and did not have the chance to read your message earlier.

Are you still looking for a solution to this problem?

Regards

Joachim

• Hello Joachim,

I have the same doubt that Ramki. I want plot using differents dataset having differents number of rows.

• Hello Joachim, I need your help. Do you know how to comine two pltos froms differents data frames (two different models of the library effects) For example:
library (nlme)
library (effects)
m1<- lme(log(Ara_Tot+1) ~ FOREST+log(Ara_Tot_m+1)+log(Prey_ChinchFit_Lepidop+1), data= REDV, random = ~1|ANIO, method ="REML")
eff_Forest<- effect("FOREST",m1, partial.residuals=TRUE)
plot(eff_Forest, smooth.residuals=FALSE,lty=1,lines=list(col="black",lwd=2), residuals.color="black",band.colors="black",band.line ="black",lwd=3, main="Spiders, Before b. pod", ylab="% of forest")

m2<- lme(log(Ara_Tot+1) ~ FOREST+log(Ara_Tot_m+1), data= PANV, random = ~1|ANIO, method ="REML")
eff_Forest<- effect("FOREST",m2, partial.residuals=TRUE)
plot(eff_Forest, smooth.residuals=FALSE,lty=1,lines=list(col="black",lwd=2), residuals.color="black",band.colors="black",band.line ="black",lwd=3, main="Spiders, Before b. pod", ylab="% of forest")

I want to show in one graphic both variables of these two differents models.

Could you help me??

• Hey Silvana,

Are you looking for the points() function? Please have a look here for more details.

Regards,
Joachim

• Thank you Joachim! I wil try, but I think effects library cannot run with this option!
Best regards, Silvana

• It seems like you have used the plot function to draw your data before. I assume that the point function works as well, if the plot function works.

Regards,
Joachim

• Hi, I have two data frame, both with the same number of columns, all named year, model and rain.
But while in data frame 1 has four differents values in the column model (like model1, model2, model3, model4), the data frame 2 has only one value (model5).
I want to plot a chart comparing the rain of each model of data frame 1 with the model of data frame 2 separetly.
It would appear four panel comparing: model1xmodel5, model2xmodel5, model3xmodel5 and model4xmodel5

• Hello Pedro,

I was on vacation. Do you still need help?

Best,
Cansu