Stata allows us to code different types of numeric missing values. It has 27 numeric missing categories. In this page we will show how to code missing values into different categories. First we create a data set for the purpose of illustration. In this data set, all the variables are numeric and the variables female and ses have missing values. The non-missing values for variable female is 0 for male and 1 for female.
Missing Values | Stata Learning Modules
The non-missing values for variable ses is 0 low1 med and 2 high. The rest of the values are considered to be missing values. For example, for variable femalewe can do the following:. The codebook command above shows that variable female has three types of missing values and 4 missing values.Dummy Variables using the gen command in Stata
Method 1 may not be the best way of recoding missing values into different categories. For one thing, we have to do it one variable at a time. The other issue that we will cover here is how to change missing value codes back to numeric values. The command mvencode is paired with command mvdecode that we just covered above and is the one to use here. Click here to report an error on this page or leave a comment Your Name required. Your Email must be a valid email for us to receive the report!
How to cite this page. Method 2: Using command mvdecode Method 1 may not be the best way of recoding missing values into different categories. Click here to report an error on this page or leave a comment.Search everywhere only in this topic.
Advanced Search. Classic List Threaded. Replace missing values by 0.
These missing values i would like to replace by 0 zero. What command can i use to do this? Thanks in advance for your support. Martin Weiss AW: Replace missing values by 0. Tirthankar Chakravarty. Re: Replace missing values by 0. In reply to this post by Hobst.
Regards This is a very basic question though. Neil -- "One should as a rule, respect public opinion in so far as is necessary to avoid starvation and to keep out of prison, but anything that goes beyond this is voluntary submission to an unnecessary tyranny, and is likely to interfere with happiness in all kinds of ways AW: st: Replace missing values by 0.
Nick Cox. RE: Replace missing values by 0. In reply to this post by Tirthankar Chakravarty. I have one specific and one general comment here.
Specifically, Martin is correct to underline that. One of the very first entries, to [I] missing values, answers this question comprehensively, so it is difficult to see why it was felt necessary to send it to Statalist.Why Stata?
Supported platforms. Stata Press books Books on Stata Books on statistics. Policy Contact. Bookstore Stata Journal Stata News. Contact us Hours of operation. Advanced search. Users often want to replace missing values by neighboring nonmissing values, particularly when observations occur in some definite order, often but not always a time order. Typically, this occurs when values of some variable should be identical within blocks of observations, but, for some reason, values are explicitly nonmissing within the dataset only for certain observations, most often the first.
So, there is a wish to copy values within blocks of observations. Alternatively, users often want to replace missing values in a sequence, usually in a time sequence.
These problems can be solved with similar methods.
Stata: Data Analysis and Statistical Software
A different situation, not addressed directly in this FAQ, is when values of some time-varying variable are known only for certain observations. There is then a need for imputation or interpolation between known values. Copying the last value forward is unlikely to be a good method of interpolation unless, as just stated, it is known that values remained constant at a stated level until the next stated level. Either way, users applying the methods described here for imputation or interpolation take on the responsibility for what they do.
Note that all the interpolation methods mentioned here and some others are directly implemented in the community-contributed command mipolate which is downloadable from SSC. Let us first look at the case where you have not tsset your data see, for example, [TS] tsset for an explanationbut we will assume that the data have been put in the correct sort order, say, by typing. There is not, of course, any observation before the first, or after the last, so myvar is always missing, as is myvar for any observation number that is negative or greater than the number of observations in the data.
See [U] If myvar is numeric, you could write. Most problems involve missing numeric values, so, from now on, examples will be for numeric variables only.Login or Register Log in with. Forums FAQ. Search in titles only. Posts Latest Activity.
Page of 1. Filtered by:. Marco Araujo. My dataset has missing values in more than 15 variables they are newly generated variables and I need to replace them by zeros. Is there any command I can use to just input zeros whenever value missing, without having to specify varlist? Tags: None. Comment Post Cancel. Steve Samuels.
Replace missing values by 0
Exactly why do you need to replace missings by zero? The only circumstance I know of where this is justified is when answers are missing because of a skip pattern in a questionnaire. If, for example, the answer to a question "Do you smoke cigarettes" is "No", all further questions related to cigarette smoking are skipped. This includes a question about the "number smoked per day", which for non-smokers is zero. Please also note the strong preference on Statalist for full real names on Statalist, a long-standing practice that contributes to professionalism and collegiality on the list.
Please re-register with a username that includes your full names, first and last; use the Contact Us button on the bottom of the page. Steve Samuels Statistical Consulting sjsamuels gmail. Thank you for your assistance. Actually, I am not completing zeros for survey data.
I should have explained in more detail what I was doing, but here it is. Thank you Ben Earnhart. I am gonna try to modify the username.This module will explore missing data in Stata, focusing on numeric missing data. It will describe how to indicate missing data in your raw data files, as well as how missing data are handled in Stata logical commands and assignment statements.
We will illustrate some of the missing data properties in Stata using data from a reaction time study with eight subjects indicated by the variable idand the subjects reaction times were measured at three time points trial1, trial2 and trial3. The input data file is shown below.
You might notice that some of the reaction times are coded using a single. As a general rule, Stata commands that perform computations of any type handle missing data by omitting the row with the missing values. As you see in the output below, summarize computed means using 4 observations for trial1 and trial2 and 6 observations for trial3. In short, the summarize command performed the computations on all the available data.
A second example shows how the tabulation or tab1 command handles missing data. Like summarize, tab1 uses just available data. Note that the percentages are computed based on the total number of non-missing cases.
It is possible that you might want the percentages to be computed out of the total number of observations, and the percentage missing for each variable shown in the table. This can be achieved by including the missing option which can be shortened to m after the tabulation command. We would expect that it would perform the computations based on the available data and omit the missing values.
Here is an example command. The output is show below. Note how the missing values were excluded. Stata will perform listwise deletion and only display correlation for observations that have non-missing values on all variables listed. Stata also allows for pairwise deletion. Correlations are displayed for the observations that have non-missing values for each pair of variables.
This can done using the pwcorr command. We use the obs option to display the number of observation used for each pair.
As you can see, they differ depending on the amount of missing. It is important to understand how missing values are handled in assignment statements. Consider the example shown below. The list command below illustrates how missing values are handled in assignment statements. The variable sum1 is based on the variables trial1trial2 and trial3.
If the value of any of those variables were missing, the value for sum1 was set to missing. Therefore sum1 is missing for observations 2, 3, 4 and 7. Whenever you add, subtract, multiply, divide, etc. In our reaction time experiment, the total reaction time sum1 is missing for four out of seven cases. We could try totaling the data for the non-missing trials by using the rowtotal function as shown in the example below. The results below show that sum2 now contains the sum of the non-missing trials.
Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I have a dataset of health facility caseload by year, where each observation is one health facility. Facilities were 'brought online' in different years, so some have zeros before they have values for caseload.
Also, some 'discontinue', as in they did provide services, but don't any more. I would like to replace the zeros with missing values for the years in which a facility discontinued. I tried the following, which worked, but I'm going to have many years worth of data to work onso was wondering if there was a more efficient way.
I messed around with egen rowlast to identify the facilities with a zero in the last year meaning they discontinuedbut then wasn't sure where to go with it. We'll initialise started to 0, change our mind about started when we see a positive value, and change any subsequent 0s to missings if started is 1.
A more general comment is that this is not the better data structure for such panel or longitudinal data. This particular problem is not too challenging, but most problems with such data will be easier after reshape long. See here for a survey of "rowwise" technique in Stata. Learn more. Replace zeros with missing values in certain cases Ask Question. Asked 5 years, 7 months ago. Active 5 years, 7 months ago. Viewed 7k times.
I was wondering if anyone knew an easier way of doing the following: I have a dataset of health facility caseload by year, where each observation is one health facility. Nick Cox Joshua Joshua 1 1 1 silver badge 2 2 bronze badges. Active Oldest Votes. Your problem would benefit from a loop over the variables.
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