merge is for adding new variables from a second dataset to existing observations. You use merge, for instance, when combining hospital patient and discharge datasets. If you wish to add new observations to existing variables, then see [D] append.

Easy: Stata can match on more than one variable. Just sort both datasets on both variables, then list both in the -merge- command: .

merge 1:m or . merge m:1 ; see Merge two data sets in the many-to-one relationship in Stata. To merge two data sets in Stata, first sort each data set on the key variables upon which the merging will be based. Then, use the .merge command followed by a list of key variable(s) and data set(s).

To join two data frames (datasets) vertically, use the rbind function. The two data frames must have the same variables, but they do not have to be in the same order. If data frameA has variables that data frameB does not, then either: Delete the extra variables in data frameA or.

Merge Multiple Databases into a Single Database

1. Create several smaller databases containing the core data tables.
2. Merge the smaller databases into a single larger database.
3. Build the schema/add the relevant constraints.

The syntax below does this, note that the command is the same as in the first example. By default, Stata will allow cases to come from any of the three datasets. When more than one dataset appears in the using list, merge creates additional _merge variables, one for each dataset listed in using (e.g. _merge1, _merge2).

append adds observations to the existing variables. merge adds variables to the existing observations. That is an oversimplification because merge does not require that the datasets have the same observations.

In order for Stata to merge the datasets, the id variable, or variables, will have to have the same name across all files. Once you have identified all the variables you need, and know what the id variable(s) are, you can begin to merge the datasets.

In an m:1 merge, the key variable or variables uniquely identify the observations in the using data, but not necessarily in the master data.

How do I concatenate two columns in R? To concatenate two columns you can use the paste() function. For example, if you want to combine the two columns A and B in the dataframe df you can use the following code: df[‘AB’] <- paste(df$A, df$B).

merge 1:1 n performs a sequential merge. n is not a variable name; it is Stata syntax for observation number. A sequential merge performs a one-to-one merge on observation number. The first observation of the master dataset is matched with the first observation of the using dataset; the second, with the second; and so on.

Merge one set of files (and/or the stream spec) into another. The p4 merge command is a simplified form of the p4 integrate command: it merges a set of changes from source to target files. The command outputs the scheduled resolves.

Appending two datasets require that both have variables with exactly the same name. If using categorical data make sure the categories on both datasets refer to exactly the same thing (i.e. 1 “Agree”, 2”Disagree”, 3 “DK” on both). Remember that Stata is case sensitive, ‘Year’ is not the same as ‘year’.

After merge, the merged result is left in memory. The id variable is called the key variable. Stata jargon is that the datasets were merged on id. Observations for id==1 existed in both the master and using datasets and so were combined in the merged result.