A typical example would be data collected from (many) individuals living in different countries, stored in the master dataset. The information from a case in the using dataset will be merged to each case in the master dataset with the same caseid. Merge m:1 caseid using name-of-second-datasetĪssumes that for each value of caseid in the using dataset there may be more than one case with this caseid in the master dataset. Not each caseid in one dataset has to have an equivalent in the other dataset, but unless there is a certain amount of overlap you will not be inclined to merge data. Here, "name-of-second-dataset" (called the "using dataset" by the Stata people) is merged to the data in memory (called the "master dataset"), assuming that each value of variable "caseid" is present only once in each of the data sets. Merge 1:1 caseid using name-of-second-dataset If both data sets contain one row per case, you just write: In the following I assume the presence of only one key variable, called "caseid" in my examples. The prerequisite for accomplishing this is to have, in each of the datasets involved, one or several variables that uniquely identifies or identify each case such variables are called "key variable". The challenge, of course, is to merge the datasets in such a way that information about individual A in dataset X is matched to the information about the same individual in dataset Y, and so on. When merging datasets, you will try to match different information about the same cases, information that for some reason or other is stored in more than one data set (e.g., because one part of the information was collected earlier on and additional information has been obtained later). Merge (Stata Version 11 or higher) Basics Stata will just tell you that you have used old syntax. The old syntax (described further below) will also work with newer versions that is, you don't have to rewrite all your older do files. The syntax for merging has changed as of Stata version 11. "Append" is dealt with at the bottom of this entry. To deal with this case, "append" is the command to use. Or two data sets contain (more or less) the same variables, but refer to different observations (cases, objects). This case is dealt with by the "merge" command. There are two constellations: Either two data sets refer to (more or less) the same observations (cases, objects) but contain different variables. These commands enable you to unite two or more data sets. Multiple Imputation: Analysis and Pooling Steps. Confidence Intervals with ci and centile.Changing the Look of Lines, Symbols etc.
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