合并具有不同列和行数的R DataFrame

Question

I am trying to combine 2 data frames via a column known as username. One data frame contains 12 variables with 1619 rows of observations. The other contains 37 columns with 1603 observations. I'd like to match the usernames from each data set, but keep all data. I have tried a merge, but I always get NA for the Y set of data (unless the colname is in both sets of data). Is there a way to append one set of data to another via a column name such as "username?"

Example below:

DataFrame 1
Username      HighschoolGPA     Age     Applydate
Smith, John   3.1               18      03-12-2012

DataFrame 2
Username    LiveOnCampus        Major       StudentGroup_Academic       
Smith, John  Yes                Chemistry   No              

Final DataFrame
Username HighschoolGPA Age Applydate LiveOnCampus Major StudentGroup_Academic
Smith, John 3.1         18  03-12-2012  Yes     Chemistry   No              

Answer 1

df1 <- data.frame(Username='Smith, John',HighschoolGPA=3.1,Age=18,Applydate='03-12-2012',stringsAsFactors=F);
df2 <- data.frame(Username='Smith, John',LiveOnCampus='Yes',Major='Chemistry',StudentGroup_Academic='No',stringsAsFactors=F);
merge(df1,df2,'Username');
##      Username HighschoolGPA Age  Applydate LiveOnCampus     Major StudentGroup_Academic
## 1 Smith, John           3.1  18 03-12-2012          Yes Chemistry                    No

Answer 2

You usually get NA for the Y set of the data when the merge function is matching multiple columns and generating to many unique combinations.

Make sure the username columns are the same type, make sure they aren't factors, and specify more arguments to the merge function.

Try merge(df1, df2, by = "username", all.x = TRUE, all.y = TRUE) if you would like to keep all results, matched and unmatched.

Try merge(df1, df2, by = "username", all.x = FALSE, all.y = FALSE) if you want to keep only entries that have a matched username.

Hope this helps!