This allows you to specify how you would like missing values in a string variable to b handled when autorecoded. Next, we populate the new string variables using the compute command with the substr function. But i do not want those variables to be treated as factor variables. The string variables represent answers to multiple response questions and are either dichotomous or categorical answers coded as strings. Perhaps the most important advantage is that they can be used in s. Previously i used the code cor x1 x2 when finding the correlation between continuous variables but i am not sure how to proceed when dealing with categorical variables. In stata this is often true because stata treats string encoded variables as missing and will not use them in analyses. I hope that made sense, i might not even be understanding how stata does panel data correctly. There are a number of advantages to converting categorical variables to factor variables. Like so, working with string variables in spss is super easy.
Jun 18, 2016 factor variables are categorical variables that can be either numeric or string variables. Press question mark to learn the rest of the keyboard shortcuts. In earlier versions, a string variable could contain up to 244 characters. However, when i click on analyze multiple response define variable sets i get a popup window with a warning. Transform string variable to categorical integer variable.
Complex strings may be very long and may contain binary information. This can be helpful even if factor variables are not specified. The easiest way to convert string variables to numeric form is to use the encode command. Stata as well as most other statistical packages wont use observations that are. Alternatively, you can use encode to convert string categorical variables to. This command can replace loops where a manual check is done to see if the specified variable is contained in eb andor ev. It is obsolete xi has been replaced by explicit support for factor variables since stata 11 and numerically cumbersome use xtreg, fe or areg instead. You can, however, extract one or more characters a substring from them, glue them together concatenate and a couple of other functions. Stata is not sold in modules, which means you get everything you need in one package. This allows you to specify how you would like missing values in. If you have more than 67,784 unique values of the string variables that you are encoding, encode will complain. All indicator variables are categorical variables, but the opposite is not true.
When i run this from my dofile, after the first set of dydx output i get the. There are a few reasons why you may not be able to see your variables in some of the spss dialog boxes. On april 23, 2014, statalist moved from an email list to a forum, based at. I think thatd likely work well as long as cross operators arent used, for example, c. Factor variables refer to statas treatment of categorical variables. The command set more off tells stata not to pause or display the more message. The following document provides an example of how to create. Jul 28, 2009 when cleaning datasets one often has string variables containing categories e. As an example, the german word fur is a string of length three in stata, but the string length is four in stata 14. The main problems that may arise and their possible solutions are surveyed with reference both to official stata and to userwritten programs.
But with statas datetime features, some computations, as well as the representation of data to the human eye and mind may become easier. There may be times that you receive a file that has many or all of the variables defined as strings, that is, character variables. Listing nonmissing string variables in stata stack overflow. Entering factor variables in regressions in stata factor variables are a way to quickly enter dummy variables or interactions in a regression model in stata without creating new variables first. This module may be installed from within stata by typing ssc install factmerg. Dates in string form, identifiers and categorical variables, and pure numeric content trapped in string form need different actions. I know somebody has asked this question before, but i found the answers to be unhelpful. Christopher f baum boston collegediw factor variables and marginal effects jan 2010 7 18. Choose which interaction to omit using factor variables and fixed effects hot network questions product of 2 uniform random variables is greater than a constant with convolution. One method of converting numbers stored as strings into numerical variables is to use a string function called real that translates numeric values stored as strings into numeric values stata can recognize as such. Encode assigns numerical values 1, 2, to newvar, while the original values e. Since both are of the form 22xxx, i want to assign value 1 for both in the variable. I want to collapse the data in stata such that the data appears as.
Using stata efficiently to understand your data the analysis factor. Note that modern statistical software offers a tremendous range of possibilites. Also, please do not use this syntax to estimate fixed effects regressions. One possible reason is that your variable is a string variable and the dialog box will only accept numeric variables. Before we do this, we take a random sample of 10% of the cusips. I have completed the principal component analysis pca, exploratory factor analysis efa, and confirmatory factor analysis cfa, treating data with likert scale 5level responses.
Sep 27, 2016 convert variables from string to numeric in stata duration. Factor variables are categorical variables that can be either numeric or string variables. The column provides a stepbystep guide explaining how to convert them oras the case may meritto leave them as they are. Some of these are the following use help function in stata to learn more. How can i quickly convert many string variables to numeric.
String variables that seemingly should be numeric require some care. Why is my command not working with factorvariable syntax andor collinear. How can i easily convert a string variable to a categorical. Merging string variables into one variable statalist. Why cant i see my variables in some of the spss dialog boxes. When cleaning datasets one often has string variables containing categories e. Learning to use statistical software involves a lot of trial and error, angry. Generating dummy variables from excel file into stata.
Lastly, omission of variables is not an error, but intended behavior when the design matrix is singular. However, i dont know what to do in this situation since product is a string variable. Unless you have a very old version of stata, in which case you should be telling us about it, use factor variable notation, not explicit indicator. Factor scores in approaches 2 and 3 are more difficult to estimate than factor scores in classic fa or in approach. Stata news, code tips and tricks, questions, and discussion.
But i dont think theres a command that extracts the level or base level of a factor variable or that splits a factor variable into its variable name and level. Discover factor variables and a basic introduction to using them in regression models. These variables can be used like any other numeric variables. In the third step, we create numeric versions of the string variables using the compute command with the numeric function. The next thing i like to know about my data is if any of the variables are string. You can only tell the type of a variable by using the describe command. I modify the ordinary leastsquares ols command discussed in programming an estimation command in stata. Command generate is used if a new variable is to be added to the data set. Data analysis with python and pandas convert string category to numeric values tutorial 6. We are here to help, but wont do your homework or help you pirate software. Cs6, cs6 is just a variable for education completed, but every time i try to run this regression, it says cs6. These string variables can be used in creating row labels for output tables andor plots, possibly using the sencode package. Commands that pass values into variables, most notably compute and if, can be used for both existing and new numeric variables. And, you can choose a perpetual licence, with nothing more to buy ever.
Oct 19, 2012 discover factor variables and a basic introduction to using them in regression models. If syntax varlist is used and factor variables are to be allowed in the varlist. To start this process, we first create the three string variables called m1, d1 and y1. Even so, because the variable is defined as str2, stata cannot perform any kind of. A complex string is a string that contains more than one piece of information. I may have possible issues with multicolinearity and i want to check. Ibm i cannot use string variables for creating a multiple. Now, lets say you would like to create a categorical variable that tells you. In stata this is often true because stata treats stringencoded variables as missing and.
Even though this is not typical, this variable may also appear on the right. Spss string function converts numeric values to string values. However, anticipating that this may be problematic, stata offers various commands to change string variables into categorical variables and vice versa. All variables in the working file or in variable sets in use are inappropriate for this. How can i quickly convert many string variables to numeric variables. A simple way of transforming such a variable to one variable containing the same information is encode. If you have a string variable and want to convert it to a numeric variable, you can use the encode command. Stata is a complete, integrated software package that provides all your data science needsdata manipulation, visualization, statistics, and automated reporting. Also factor variables are supported in most official stata commands, and communitycontributed commands will need to understand this new syntax for factor variables to be accepted. They have an added benefit in that postestimation commands better understand the components of your model. There are no system missing values in string variables. A better ols command to allow for sample restrictions, to handle missing values, to allow for factor variables, and to deal with perfectly collinear variables. If the variable is actually a numeric value that just happens to be stored as a string, see our faq.
With string variables, stata has only one definition of missing, namely that a string is empty, and contains precisely no characters. How can i convert string variables into date variables. The first case most often occurs when importing data from another source. The variables may contain numeric values, but if they are defined as type string, there are very few things you can do to analyze the data. One or more spaces, despite usually conveying nothing to people, do not qualify as missing so far as stata is concerned. However my variables are categorical and coded 0, 1, 2, 4 etc. Odd numbers of characters in string variables were soon allowed in stata 2. The first line of syntax reads in the dataset shown above. It seems that stata automatically treat some data as factor variables. Keywords pr0006, binary variables, categorical variables, data editor, dates, decode, destring, encode, identifiers, missing values, numeric variables, spreadsheets, string functions, string.
Various steps are required to allow factor variables to be specified with a command and to correctly handle the new collinearity behavior. This is the eighth post in the series programming an estimation command in stata. Then, using lavaan, i repeated the cfa defining the variables as categorical. Another possibility is that your variable has a different measurement. Again, im new to stata, but how woud i go about telling stata to treat a flight, or any x variable, as only explaining a change in the y variable a week or so later. Reed college stata help changing string variables to. Im not sure whether bambi is working with cross operators, but a single factor variable that uses a cross operator can actually involve multiple base variables.
However, they cant be used for new string variables. Stata handles factor categorical variables elegantly. Stata will assume that both variables are to be treated as categorical if there is no prefix. The first tabulate looks identical to the tabulate done on the string variable region above. I have a dataset with string variables and i am trying to generate a new binary variable based on the first two characters. Create factor dummy variables from a long variable statalist. In stata this is often true because stata treats stringencoded variables as missing and will not use them in analyses.
I am aware that if product were a numeric variable we could use the collapse command. I have a data file which contains string variables only. How can i convert string variables to numeric variables in. In order to see what a string variable looks like, we can use the converse command. An example of when one might need to do this is if they needed to append. Factor variables hey, i am currently running the regression reg ws8hourly i. All strings are 5 characters long, but im only concerned with the first two in order to sort. Categorical variables refer to the variables in your data that take on categorical values, variables such as sex, group, and region. Stata module to merge a list of factors to create string variables, statistical software components s419602, boston college department of economics, revised 20 apr 20. As you can see from the second tabulate, region2 has the numeric values 1 through 4 but retains the strings central, east, south and west as value labels. Irt fitting certainty quickly decreases as the number of factors grows, which is a problematic side of this approach. So long as you have the variables that you used in creating the dummy variables, i consider it much more appealing to import your entire dataset into stata and generate the dummy variables there. Changing string variables to categorical variables and vice verse.
This also influences the results of functions such as strlen. You cant use numeric functions such as addition or subtraction on string variables. As strlen refers to the memory used and not the number of characters as they appear on the screen, the result of strlenfur will also be 4 in stata 14 in. To create new variables typically from other variables in your data set, plus some arithmetic or logical expressions, or to modify variables that already exist in your data set, stata provides two versions of basically the same procedures. String variables can have a length of 1 to 244 characters. Now that we know the variables are string variables, we can use the list. You cannot get means, you cannot do a regression, you cannot do an anova, etc. The following document provides an example of how to.
323 1166 516 1392 570 1487 1186 822 365 608 938 1419 885 144 331 1256 125 480 1093 1284 717 1093 789 105 1118 668 888 658 901 1024 969 157 578 1336 27 1112