R - Using ggplot2 with two data sets of different sizes

0
votes

I want to do a scatter plot for two datasets with different sizes.

Imagine I have two data.frames: df1, df2. The row size of df1 is 100, and of df2 is 50. Is there a way to do a scatter plot with ggplot2? I've searched but couldn't find anything. The online tutorials always assume that the datasets are of the same size, with equal value for the x-axis. Also, I want to plot the two datasets in the same graph, not side-by-side.

Here's some exemplifying data:

df1<-data.frame(X1=1:10,Y11=11:20,Y12=21:30,Y13=31:40)

df2<-data.frame(X2=1.5:10.5,Y21=1.5:10.5)

Let's imagine X1 is a column with values measuring distance in km. Y11 is the vector with values for fuel consumption for Car1, Y12 is the vector with values for fuel consumption for Car2, and so on. Now X2 is still vector with values measuring distance in km, different from X1, but in the same range. Y21 is the fuel consumption for a modified Car1. I want to put them in the same scatter plot, with x-axis being distance(km) and y-axis being fuel consumption

4
rplotggplot2
This shouldn't be any problem. Just pass the data directly to the geom_point() layers. It would helpful if you provided a reproducible example with sample input data and the code you tried. We could then offer specific fixes. - MrFlick
@MrFlick I've edited the question and included some data. I didn't write the code I've used since I fail right at the beginning where we have to give just one data.frame to the ggplot command. - An old man in the sea.
Exactly which values do you want to plot from the sample data? It's unclear how you would want to visualize df1 with it's 4 columns. - MrFlick
@MrFlick I want to plot the points of the type (X1,Y11),..., (X1, Y13), and also those of the type (X2,Y21) in the same graph - An old man in the sea.
But you want to treat all those values in df1 as "one" scatter plot? You you basically want to ignore the columns? I'm getting more confused as to what the desired output here. - MrFlick

4 Answers

0
votes

This would be much easier to answer if you gave an example data set. but here is what you can do (make sure each data.frame has the same column names):

df1 <- data.frame(x = 1:50, y = 1:50)
df2 <- data.frame(x = 100:1, y = 1:100)

df1$cat <- "df1"
df2$cat <- "df2"

df <- rbind(df1, df2)

library(ggplot2)
ggplot(df, aes(x, y, color = cat))+
  geom_point()

and that gives you this: enter image description here

0
votes

If you want to plot all the data together, then It's best to reshape your data. Here's an example using other tidyverse functions

library(tidyr)
library(dplyr)

dd <- bind_rows(
  df1 %>% gather(car, mpg, -X1) %>% rename(X=X1),
  df2 %>% gather(car, mpg, -X2) %>% rename(X=X2)
)

ggplot(dd, aes(X, mpg, color=car)) + geom_point()
0
votes

It's an old question, but recently I have solved a similar problem using a quicker approach than the ones here

ggplot with 2 y axes on each side and different scales

Maybe you can first scale down one of the datasets, and then try out the "dual y-axes" function in ggplot2, namely,

p <– ggplot2(dataframe, ...)+...
p + scale_y_continuous(name, ..., sec.axis = sec_axis(...))

where sec.axis means "the second axis" Please refer to https://www.r-graph-gallery.com/line-chart-dual-Y-axis-ggplot2.html for details. ?sec_axis in R also helps.

-1
votes

Thanks to a comment by MrFrick, I think I got it.

ggplot(data=df1) + geom_point(aes(x=X1,y=Y11, 
                          color="Car1"))+
  geom_point(data=df2,aes(x=X2,y=Y21),color="ModCar2"))