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I have two tables that are in the data.frame structure. Table 1 contains a column of 200 gene IDs (letters and numbers) and Table 2 contains a list of 4,000 gene IDs (in rows) as well as 20 additional columns. I want to intersect these two tables and generate a new Table 3 that contains the 200 gene IDs as well as the associated information in the 20 columns.

table3 <- table1%n%table2

Jordan
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    Welcome to SO! Please read [ask] and [mcve] ... then **edit your question!** – jogo Dec 07 '17 at 15:09
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    Welcome to SO. Your question is really about a well-documented task. You can have a look to `left_join` and `right_join` from the package `dplyr` – nghauran Dec 07 '17 at 15:10

2 Answers2

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You want something like 

table3 <- merge(table1, table2, by.x="id", by.y="id", all.x=T, all.y=F)

You might also be able to do subsetting with something like this:

table3 <- table2[table2$id %in% table1$id,]

A reprex would have made this post more likely to get a good response, but you should have been able to find something to help you with a little searching. If these don't work because you have a unique problem no one has asked before, give is a reprex and we can try to give you alternative solutions.

edit: for a little more context, here's a similar question I replied to last week and here's a great post on understanding merges.

cparmstrong
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    Thanks so much. I cannot tell you how much I was searching before your post to this. Definitely learning how to search this awesome resource better. Thanks again. – Jordan Dec 19 '17 at 15:02
  • I've learned that one of my most valuable skills is not being able to solve problems but knowing the keywords to search for to find others' solutions to my problems. – cparmstrong Dec 19 '17 at 16:39
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I recommend the dplyr package. It works more intuitively than merge in my opinion.

you can just type:

table3 <- left_join(table1, table2, by = "unique_id")
dasds
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  • OuterJ <- merge(x = Oct, y = Sept, by = "CONTACT_ID", all = TRUE) LeftJ <- merge(x = Oct, y = Sept, by = "CONTACT_ID", all.x = TRUE) RightJ <- merge(x = Oct, y = Sept, by = "CONTACT_ID", all.y = TRUE) CrossJ <- merge(x = Oct, y = Sept, by = NULL) – ASH Dec 19 '17 at 18:36