Missing values for string variables are handled similarly to the missing values for numeric variables. A string representing a categorical variable stata. By default all observations with missing values are removed from analysis. The module identifies missing value in numerical and string variable. Fortunately, stata offers some easy ways for converting string to numeric variables and vice versa. If there are missing observations in your data it can really get you into trouble if youre not careful. Otherwise, you can use encode to convert string data into a numeric variable or decode to convert numeric variables to strings. Its a common mistake when importing data to accidentally make stata think a numeric variable is a string. Different statistical software code missing data differently. I would try method 3, but generate a new variable to see where exactly stata thinks there are missing values and add the force option. You can only define missing values for string variables whose length is eight or less what spss calls short string variables.
Replacing string variables to missing 26 mar 2017, 11. This module should be installed from within stata by typing ssc install multencode. Changing string variables to numbers in stata pradeep ramulu. You claimed that missing values were represented by. I have 970 obs in one variable and 270 obs in the other variable. Value labels will be defined for numeric variables.
Its evidently a numeric variable, but you are seeing the value labels. Coincidentally, i was working on a stripolate program earlier today. Most statistical programs including sas, spss, and stata will automatically remove. This value can be one or more blanks, or a numeric code such as 9999. These commands rely on value labels, which are described below. With string variables, stata has only one definition of missing, namely that a string is empty, and contains precisely no characters. Options for mi impute mvn change the number of iterations change the prior distribution categorical variables categorical variables cont. Missing values for string variables are denoted by empty string. Should be a string value is missing if and only if it is empty.
Missing data values will affect how stata handles your data. However, unlike numeric variables, empty fields in string variables are not designated as system missing. How can i see the number of missing values and patterns of missing. Apr 12, 2014 in destring complication, anup asked how to split a string variable. If we want to mark all the observations for which at least one identi. Variables may either be recoded into numeric variables or into string variables.
If it reports 0 real changes made, then stata is probably not resposible for the blanks. If a range is used, a single discrete missing value can be added to it. In his case, he has a variable of the form 28180018021832ob where 28 represents state code, 18 represents districts code, 0018 represents subdistricts code and 02183100 represents village code. Unfortunately, i have missing values in the original variable. Summary of how missing values are handled in stata procedures. Rather, they are left blank and spss does not consider them to be missing. Dec 01, 2016 this video demonstrates how to convert categorical string variables to labeled numeric variables. Like other statistical packages, stata distinguishes missing values. One or more spaces, despite usually conveying nothing to people, do not qualify as missing so far as stata is concerned. That is, the function missing returns 1 for true with string arguments if. Stata is a popular statistical program at the sscc that is used both for research and for teaching statistics.
If you are working with string variables, the data will appear as blank. Stata module to transpose string variable dataset, statistical software components s446402, boston college department of economics. In contents of the variable choose fill with missing datayoull type in the real values later. In stata this is often true because stata treats string encoded variables as missing and will not use them in analyses. Data manipulation and analysis it services 2 note the. In stata this is often true because stata treats stringencoded variables as missing and will not use them in analyses. If you recorded the missing values for a string variable using some kind of nonblank indicator for example, 999 or 999 and have already defined that user missing value in the variable view window, automatic recode will preserve the missing designation, but will still convert the category code to be in the range of the other categories. Var2 is a string variable even though you see numbers. 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. In stata, if your variable is numeric and you are missing data, you will see. For the case of numerical variables, also statacoded missing values e. Use a quotes when var2 is a string and no quotes when the var has numeric formatting. Stata module to generate an index of terms from string variable, statistical software components s457993, boston college department of economics, revised apr 2019. Need help with converting string variables to numeric variables.
That output strongly resembles what spss produces, and is about the only thing i recall liking better in spss than in stata. If i am not mistaken, until version 8 there was only one missing value, the dot. Not least, most statistical procedures just do not accept string variables. This will make sure any missing values of the original string indicator variable wont get coded as 0. Most statistical programs including sas, spss, and stata will automatically.
Any string in var that does not meet the conditions of rules is set to missing in created numeric variables and copied from var in created string variables. However, if i want to do it with strings, stata reports r109 type mismatch. The,replace at the end just means that if a log file of this name exists in this folder then write over it this is useful if you are running the syntax for a project multiple. Stata for students is focused on the latter and is intended for students taking classes that use stata. It returns a new dataset containing a string variable listing the terms and a numeric variable with the corresponding frequencies. Stata news, code tips and tricks, questions, and discussion. I usually work in r, but i have to use stata this time, thats why im struggling with this commercial software. I am trying to figure out how to decide which variable to use to impute on in my dataset. Hence the new variable generated with destring command and force option. A thing to note, however, is that missing values can be specified for multiple variables at once. Although the variable science is defined as str2, you can see from the list below that it contains just numeric values. R converting r file to stata with missing string values. Perhaps unsurprisingly, missing values can be specified with the missing values command.
Lets now use recode to assign letter grades to ranges of the total score. I have a string variable with abbreviations for different sectors. To indicate a missing value in a string variable, you need to use the missing values command and assign a value to missing cases. The term blank is perhaps unclear here and thus better avoided. On april 23, 2014, statalist moved from an email list to a forum, based at.
The snippet i provided will give you a 1 when var2 is not missing data and a 2 when data is missing. With a force option, datasets containing numeric variables may also be transposed. We are here to help, but wont do your homework or help you pirate software. Command generate is used if a new variable is to be added to the data set. The first line of syntax reads in the dataset shown above. This video demonstrates how to convert categorical string variables to labeled numeric variables. In stata, this can be done by using either gen or egen. How can i replace missing values with previous or following nonmissing values or. I have three outcomes that i am looking at and one of the outcomes is 23% missing, whereas the other two have close to 8%.
Stata module to generate an index of terms from string variable, statistical software components s457993, boston college department of economics, revised apr. Click the variable view tab at the bottom of the data editor window. Point the cursor to the first cell, then rightclick, select zpaste. In destring complication, anup asked how to split a string variable. Stata uses certain values of variables as indicators of missing values. Press question mark to learn the rest of the keyboard shortcuts. For similar reasons, i wish that nolabel was the default option on list and browse for any new user. Reed college stata help changing string variables to. Listing nonmissing string variables in stata stack overflow. Most problems involve missing numeric values, so, from now on, examples will be for numeric variables only. First, use describe to reassure yourself that it is a string. So here string var is the variable name, and date format it where you tell stata how the date is formatted, so in your second dataset it would be day, month, year so you would put dmy with quotes as the second argument. Hello, i want to fill missing strings by using the last observation. Even though stata can handly string variables, it is clear in many respects that numeric variables are much preferred.
Second, missing values may be specified as a range. Oct 05, 2010 to concatenate is to join the characters of 2 or more variables from end to end. However, the presence of missing data can influence our results, especially when a dataset or even a single variable, has a high percentage of values missing. 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. Unlike missing values for numeric variables, missing values for string variables are not assigned a period. If you know of missing items citing this one, you can help us creating those. The missing value could be represented by the string. Stata module to identify variables with problematic. For linear regressions the areg function offers a partial solution for my issue, but that function only allows me to absorb a single factor variable. As with most things theres a lot more to learn check help missing and help cond for more details. Changing missing values in string variable it didnt work.
Changing string variables to numbers in stata youtube. How to create a date variable from a date stored as a string. As example, suppose we have the variables var1, var2, and var3. If you recorded the missing values for a string variable using some kind of nonblank indicator for example, 999 or 999 and have already defined that usermissing value in the variable view window, automatic recode will preserve the missing designation, but will still convert the category code to be in the range of the other categories.
Stata module to encode multiple string variables into numeric, statistical software components s456993, boston college department of economics, revised 21 jan 2009. Even so, because the variable is defined as str2, stata cannot perform any kind of numerical analysis of the variable science. I would also add the ignore option just in case it complains about commas being nonnumeric. To concatenate is to join the characters of 2 or more variables from end to end. Since a main issue of missing values is that it might introduce a sample selection problem, fmiss offers a very simple and purely introductive way to detect such problems. His problem is how to extract the state, districts, etc. However, anticipating that this may be problematic, stata offers various commands to change string variables into categorical variables and vice versa. I want generate a new varibale that display the words found in the string variable that match my local list of words.
Stata module to recode string variables according to. Note that there are five missing values of total because there are five missing values of science. Then, in stata type edit in the command line to open the data editor. For example the code 01400 f tells stata to recode all values of total between 0 and 140 to 0, and then give the label f to the value 0. Typically, this occurs when values of some variable should be identical within blocks of. Software steps for mcmc in stata mcmc with stata stata output 1 stata output 2 formulas imputation with the dependent variable should missing data on the dependent variable be imputed. Replacing string variables to missing statalist the stata.
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