How do I combine 3 sets of data that are different variables into 1 table?

[ksci]

merge(mydat, res, dat by.x = "ID", by.y = "seq") This is what i have so far but it is not working.

[HanOostdijk]

I assume that you are talking about the merge function from the base package.
Then as far as I know you have to do the merge in steps:
first merge data.frame1 with data.frame2 and then merge the result with data.frame3 .

[ksci]

How would that code look like?

[FJCC]

Here is an example with extra print statements to illustrate the process.

DF1 <- data.frame(ID=c("A","B","C"), Value = 1:3)
DF2 <- data.frame(Seq = c("B", "A", "C"), Number = 11:13)    
DF3 <-  data.frame(Seq = c("C", "B", "A"), Number2 = 21:23)    
DF1
#>   ID Value
#> 1  A     1
#> 2  B     2
#> 3  C     3
DF2
#>   Seq Number
#> 1   B     11
#> 2   A     12
#> 3   C     13
DF3
#>   Seq Number2
#> 1   C      21
#> 2   B      22
#> 3   A      23
AllDat <- merge(DF1, DF2, by.x = "ID", by.y = "Seq")
AllDat
#>   ID Value Number
#> 1  A     1     12
#> 2  B     2     11
#> 3  C     3     13
AllDat <- merge(AllDat, DF3, by.x = "ID", by.y = "Seq")
AllDat
#>   ID Value Number Number2
#> 1  A     1     12      23
#> 2  B     2     11      22
#> 3  C     3     13      21

^{Created on 2022-04-09 by the reprex package (v2.0.1)}