Merging two Data frames in R?-CodePudding

I am new to R and facing this problem (it may be very basic so pardon me). I have looked through the left/right merges and data.table merges but haven't had success.

Dataset1: 
Fips     County    Date          Result 
21001    Adair     01-03-2004    0.008 
21175    Morgan    11-21-2002    0.076

Dataset2:
Fips     County    Date          Pre
21001    Adair     01-03-2004    2.08
21001    Adair     01-04-2004    0.076
21001    Adair     01-04-2004    4.76
21017    Bourbon   01-03-2004    0.067
21175    Morgan    11-21-2002    0.076
21175    Morgan    05-04-2004    1.54
21175    Morgan    07-04-2004    0.008
21175    Morgan    11-21-2006    0.076

Desired_output:
Fips     County    Date          Result      Pre
21001    Adair     01-03-2004    0.008       2.08
21175    Morgan    11-21-2002    0.076       0.076

This is the code I am using:

Desired_output <- merge(Dataset1, Dataset2, by.x=c("Fips", "Date"), by.y=c("Fips", "Date"))

But it isn't giving me the desired output. It's just combining everything in the two datasets together?

Any help will be appreciated!

CodePudding user response：

If I've understood the question then this should work:

library(dplyr)
left_join(Dataset1, Dataset2, by=c("Fips", "County", "Date"))

There is a description of the different types of joins here:

CodePudding user response：

You can use an inner_join to get your desired result:

inner_join(): includes all rows in x and y.

Code:

Dataset1 <- read.table(text ="Fips     County    Date          Result 
21001    Adair     01-03-2004    0.008 
21175    Morgan    11-21-2002    0.076", header = TRUE)

Dataset2 <- read.table(text = "Fips     County    Date          Pre
21001    Adair     01-03-2004    2.08
21001    Adair     01-04-2004    0.076
21001    Adair     01-04-2004    4.76
21017    Bourbon   01-03-2004    0.067
21175    Morgan    11-21-2002    0.076
21175    Morgan    05-04-2004    1.54
21175    Morgan    07-04-2004    0.008
21175    Morgan    11-21-2006    0.076", header = TRUE)

library(dplyr)
inner_join(Dataset1, Dataset2)
#> Joining, by = c("Fips", "County", "Date")
#>    Fips County       Date Result   Pre
#> 1 21001  Adair 01-03-2004  0.008 2.080
#> 2 21175 Morgan 11-21-2002  0.076 0.076

^{Created on 2022-07-16 by the reprex package (v2.0.1)}