# subset of observations stata

(We will mention just once that it may be easier to use command line (section 1) or an option argument (section 2) may be. to give only one example, unbroken sequences of integers may be specified problems discussed here, the useful product is the intersection, not the use c:\stata\data\cancer, clear nolabel If you may want only subset of a dataset loaded, specify variables and/or observations to be read. example implies. However, the result is only a coincidence. I have a dataset, and I wish to work with a subset of observations, and that You may need to get around a mental block that There is another way to approach selection whenever Change registration Hello, I am trying to do some data cleaning in R. I need to drop observations that take on certain values of a variable. drop You can use the keep and drop commands to subset variables. observations for some of those identifiers. concisely. But most of the time "expression" will contain mathematical operators, such as in the following example: gen pcincome = income / nhhmembers That is, a variable "per capita income" is created by dividing the total income by t… quietly reg y x1 x2 x3 local subset if e (sample) list Unit `subset' reg y x1 x2 if `subset' x3 has missing values, so some observations are excluded in the first reg command. Stata/MP With 400,000 observations in the main file and 300 in the reference file, it takes about 1.5 minutes. Books on statistics, Bookstore We can also use -keep- and -drop- commands to subset data by keeping or eliminating observations that meet one or more conditions. Which Stata is right for me? Visit the Status Dashboard for at-a-glance information about Library services. The result of OBS= appears to be how many observations to process, because the output consists of 10 observations, ending with the observation number 12. Repeated typing of various Kit provided helpful comments for this FAQ as well. Stata normally has exactly one data set in memory, and commands act on that data set. you would not want to type in a dataset containing all the individual Change address We use the census.dta dataset installed with Stata as the sample data. Follow-Ups: . Because Stata numbers observations starting from 1, _N is also the observation number of the last observation. keep dataset" plus "that dataset". Now Stata tells us we have deleted another 21 observations, which we can confirm by looking at the number of observations listed by describe, which is now obs: 48. CLIR Postdoctoral Fellow your data in order to create subsets?, The statement is called subsetting because the result is a subset of the original observations. We'll find that useful as well. In this case, the census.dta is a small dataset with only 50 rows/observations in it, and I eliminated 33 observations so I know I only have a fairly small number of cases to be listed in the output. If we think of your data like a spreadsheet, this section will show how you can remove columns (variables) from your data. JavaScript must be enabled in order for you to use our website. You can cut down typing substantially by using functions such as You might wish to work with a smaller dataset In Stata, the.sample command selects random samples of the data set in memory and removes unselected observations from the data set. This function is similar to using inlist() or Worked Example 2: In this example I will demonstrate using the use command to subset your data. (This might be a long list of identifiers or some other codes specifying which observations belong in the subset.) Here is an alternative: In other words, the numlist command expands the abbreviated Stata is a good tool for cleaning and manipulating data, regardless of the software you intend to use for analysis. Let’s illustrate this with the auto data file. numlist. This method is free of any limits imposed by restrictions on how long a argument of values() may be a on the complementary subset, rather than using statsby is commonly used to graph such data in comparisons of groups; the subsets and total options of statsby are particularly useful in this regard. merge is a command that produces larger datasets; i.e., "this The first statement uses the They are particularly useful when using _n and _N Using _n Simple Usage _n is a system variable.Its value is always the current observation being worked with. First, load a data set, and then run the following command with the count option:. Subscribe to Stata News Then we keep observations 1 to 20, dropping everything else. subset is defined by a complicated criterion. the names of one or more variables) the command will only act on those variables. New in Stata 16 help limits. Again, line 3 sets up a place for to store the data. But in general, researchers do not like erasing data. We can use the describe command to see its variables. those individual elements into local macros, and the other commands then There are 13 variables in this dataset. methods. Hint: there are four different groups.) Use the -if- qualifier to subset records, to the extent they do not have cross-observation restrictions. Clearly, inrange(). I can't test this with double the observations in the main file because the lack of RAM takes my computer to a crawl. particular regulation, which fall only into certain industries). See also the FAQ How do you efficiently define group characteristics in Let’s look at a linear regression: lm (y ~ x + z, data=myData) Rather than run the regression on all of the data, let’s do it for only women, or only people with a certain characteristic: lm (y ~ x + z, data=subset (myData, sex=="female")) lm (y ~ x + z, data=subset (myData, age > 30)) The subset () command identifies the data set, and a condition how to identify the subset. For example, we can keep the states in the South. The Stata Blog Proceedings, Register Stata online numlist, so, This example uses the example data set auto.Line 1 will load the dataset. Selecting observations on the other hand usually uses logic like GENDER="F" to select all the females. sample 100, count View the entire collection of UVA Library StatLab articles. Now let’s use -drop- to eliminate those states with population below the average. Sorts the observations in a specified order of a variable, and then keeps the observations in a specified range. Note region is an integer type of variable with a value label called cenreg indicating the four regions. It is just that you really would rather not type out some long Best subsets regression fits all possible models and displays some of the best candidates based on adjusted R-squared or Mallows’ Cp. Applying commands to a subset of observations usingif Suppose we want to compute the average wage, but only for men. The functions mod() and round() are also covered at the end for your reference. Stata Press Upcoming meetings If I wanted to perform a regression on the observations of years 1994 to 1996, instead of the entire dataset, whats the command? 143–151 Speaking Stata: The statsby strategy ... r-class or e-class results across groups of observations and yields a new reduced dataset. inlist() and which was Note the clear option clears the current data in the memory, which contains the three variables we kept – don’t worry, you should still have it on your disk since we have saved it as slist.dta. Say we only need to work with population of different age groups, we can remove other variables and save as a new file called census2. In STATA I might type something like: drop if

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