Note that modern statistical software offers a tremendous range of possibilites. Why is my command not working with factorvariable syntax andor collinear. The next thing i like to know about my data is if any of the variables are string. Discover factor variables and a basic introduction to using them in regression models. However, they cant be used for new string variables. These variables can be used like any other numeric variables. Stata is a complete, integrated software package that provides all your data science needsdata manipulation, visualization, statistics, and automated reporting.
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. Categorical variables refer to the variables in your data that take on categorical values, variables such as sex, group, and region. And, you can choose a perpetual licence, with nothing more to buy ever. An example of when one might need to do this is if they needed to append. This command can replace loops where a manual check is done to see if the specified variable is contained in eb andor ev. Factor variables are categorical variables that can be either numeric or string variables. 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. I think thatd likely work well as long as cross operators arent used, for example, c. Then, using lavaan, i repeated the cfa defining the variables as categorical. 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. I have completed the principal component analysis pca, exploratory factor analysis efa, and confirmatory factor analysis cfa, treating data with likert scale 5level responses. You can only tell the type of a variable by using the describe command. There are a number of advantages to converting categorical variables to factor variables.
I have a dataset with string variables and i am trying to generate a new binary variable based on the first two characters. They have an added benefit in that postestimation commands better understand the components of your model. In order to see what a string variable looks like, we can use the converse command. All variables in the working file or in variable sets in use are inappropriate for this. Dates in string form, identifiers and categorical variables, and pure numeric content trapped in string form need different actions. Ibm i cannot use string variables for creating a multiple. Irt fitting certainty quickly decreases as the number of factors grows, which is a problematic side of this approach. 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.
How can i quickly convert many string variables to numeric. We are here to help, but wont do your homework or help you pirate software. The first tabulate looks identical to the tabulate done on the string variable region above. In the third step, we create numeric versions of the string variables using the compute command with the numeric function. In stata this is often true because stata treats string encoded variables as missing and will not use them in analyses. 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. Keywords pr0006, binary variables, categorical variables, data editor, dates, decode, destring, encode, identifiers, missing values, numeric variables, spreadsheets, string functions, string. Another possibility is that your variable has a different measurement. All indicator variables are categorical variables, but the opposite is not true. Now, lets say you would like to create a categorical variable that tells you. The command set more off tells stata not to pause or display the more message. I may have possible issues with multicolinearity and i want to check.
Transform string variable to categorical integer variable. I am aware that if product were a numeric variable we could use the collapse command. Christopher f baum boston collegediw factor variables and marginal effects jan 2010 7 18. Factor scores in approaches 2 and 3 are more difficult to estimate than factor scores in classic fa or in approach. A simple way of transforming such a variable to one variable containing the same information is encode. However, i dont know what to do in this situation since product is a string variable. 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. String variables can have a length of 1 to 244 characters. This is the eighth post in the series programming an estimation command in stata. Lastly, omission of variables is not an error, but intended behavior when the design matrix is singular. 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.
Factor variables refer to statas treatment of categorical variables. There are no system missing values in string variables. Jul 28, 2009 when cleaning datasets one often has string variables containing categories e. Merging string variables into one variable statalist. The following document provides an example of how to create. To start this process, we first create the three string variables called m1, d1 and y1. Stata is not sold in modules, which means you get everything you need in one package. Stata news, code tips and tricks, questions, and discussion. 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. Oct 19, 2012 discover factor variables and a basic introduction to using them in regression models. 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. When cleaning datasets one often has string variables containing categories e.
This module may be installed from within stata by typing ssc install factmerg. Cs6, cs6 is just a variable for education completed, but every time i try to run this regression, it says cs6. I hope that made sense, i might not even be understanding how stata does panel data correctly. Some of these are the following use help function in stata to learn more. In earlier versions, a string variable could contain up to 244 characters. If you have a string variable and want to convert it to a numeric variable, you can use the encode command.
Why cant i see my variables in some of the spss dialog boxes. As an example, the german word fur is a string of length three in stata, but the string length is four in stata 14. You can, however, extract one or more characters a substring from them, glue them together concatenate and a couple of other functions. Stata as well as most other statistical packages wont use observations that are. The easiest way to convert string variables to numeric form is to use the encode command. If syntax varlist is used and factor variables are to be allowed in the varlist. Spearman 1904 appears to be the rst to conjecture that a common unobserved trait mental ability may be responsible for the positive correlation in. Alternatively, you can use encode to convert string categorical variables to. Stata will assume that both variables are to be treated as categorical if there is no prefix. Even though this is not typical, this variable may also appear on the right.
I want to collapse the data in stata such that the data appears as. This also influences the results of functions such as strlen. Various steps are required to allow factor variables to be specified with a command and to correctly handle the new collinearity behavior. However, when i click on analyze multiple response define variable sets i get a popup window with a warning. Next, we populate the new string variables using the compute command with the substr function. How can i easily convert a string variable to a categorical. 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. A complex string is a string that contains more than one piece of information.
One or more spaces, despite usually conveying nothing to people, do not qualify as missing so far as stata is concerned. The main problems that may arise and their possible solutions are surveyed with reference both to official stata and to userwritten programs. The string variables represent answers to multiple response questions and are either dichotomous or categorical answers coded as strings. One possible reason is that your variable is a string variable and the dialog box will only accept numeric variables. But i do not want those variables to be treated as factor variables. The column provides a stepbystep guide explaining how to convert them oras the case may meritto leave them as they are. 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. Commands that pass values into variables, most notably compute and if, can be used for both existing and new numeric variables. Create factor dummy variables from a long variable statalist. String variables that seemingly should be numeric require some care. However my variables are categorical and coded 0, 1, 2, 4 etc. Reed college stata help changing string variables to.
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. This allows you to specify how you would like missing values in. Generating dummy variables from excel file into stata. Even so, because the variable is defined as str2, stata cannot perform any kind of. Press question mark to learn the rest of the keyboard shortcuts. Odd numbers of characters in string variables were soon allowed in stata 2. Data analysis with python and pandas convert string category to numeric values tutorial 6. If the variable is actually a numeric value that just happens to be stored as a string, see our faq. Stata handles factor categorical variables elegantly. Command generate is used if a new variable is to be added to the data set. On april 23, 2014, statalist moved from an email list to a forum, based at.
Changing string variables to categorical variables and vice verse. Like so, working with string variables in spss is super easy. This allows you to specify how you would like missing values in a string variable to b handled when autorecoded. Perhaps the most important advantage is that they can be used in s.
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. In stata this is often true because stata treats stringencoded variables as missing and. Jun 18, 2016 factor variables are categorical variables that can be either numeric or string variables. Before we do this, we take a random sample of 10% of the cusips. This can be helpful even if factor variables are not specified. There may be times that you receive a file that has many or all of the variables defined as strings, that is, character variables. 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. You cannot get means, you cannot do a regression, you cannot do an anova, etc. How can i convert string variables into date variables. Sep 27, 2016 convert variables from string to numeric in stata duration.
You cant use numeric functions such as addition or subtraction on string variables. It seems that stata automatically treat some data as factor variables. How can i quickly convert many string variables to numeric variables. Christopher f baum boston collegediw factor variables and marginal effects jan 2010 7. I know somebody has asked this question before, but i found the answers to be unhelpful. Also, please do not use this syntax to estimate fixed effects regressions. The first line of syntax reads in the dataset shown above. All strings are 5 characters long, but im only concerned with the first two in order to sort. The first case most often occurs when importing data from another source. Using stata efficiently to understand your data the analysis factor. Learning to use statistical software involves a lot of trial and error, angry. 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. The following document provides an example of how to. Spss string function converts numeric values to string values.
How can i convert string variables to numeric variables in. If you have more than 67,784 unique values of the string variables that you are encoding, encode will complain. When i run this from my dofile, after the first set of dydx output i get the. Now that we know the variables are string variables, we can use the list. Listing nonmissing string variables in stata stack overflow. However, anticipating that this may be problematic, stata offers various commands to change string variables into categorical variables and vice versa. Encode assigns numerical values 1, 2, to newvar, while the original values e.
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. 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. I have a data file which contains string variables only. Factor variables hey, i am currently running the regression reg ws8hourly i. There are a few reasons why you may not be able to see your variables in some of the spss dialog boxes. Since both are of the form 22xxx, i want to assign value 1 for both in the variable. With string variables, stata has only one definition of missing, namely that a string is empty, and contains precisely no characters. These string variables can be used in creating row labels for output tables andor plots, possibly using the sencode package. In stata this is often true because stata treats stringencoded variables as missing and will not use them in analyses. But with statas datetime features, some computations, as well as the representation of data to the human eye and mind may become easier. I modify the ordinary leastsquares ols command discussed in programming an estimation command in stata. Complex strings may be very long and may contain binary information.
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