If you have been working on your data in SPSS, but need to move to Mplus to complete your analysis, you can prepare and save your data in a form that Mplus can read. We will be preparing the dataset sample.sav. We can take a quick glance at the first 10 observations in this dataset.
list /cases from 1 to 10.female race ses schtyp read write -9.00 3.00 1.00 1.00 34.00 35.00 .00 -9.00 2.00 1.00 44.00 41.00 .00 4.00 -99.00 1.00 55.00 39.00 1.00 2.00 3.00 -999.00 60.00 59.00 .00 4.00 1.00 1.00 -9999.00 37.00 .00 4.00 2.00 1.00 34.00 -99999.00 .00 3.00 2.00 1.00 34.00 37.00 1.00 4.00 1.00 1.00 35.00 35.00 .00 4.00 3.00 1.00 44.00 33.00 1.00 4.00 3.00 2.00 36.00 57.00
While not a required step, running summary statistics in SPSS before moving to Mplus provides a needed reference point for checking that your data has been read into Mplus correctly. If the summary statistics you see in Mplus do not match these that were calculated before the transfer, you will know to check for errors in the process.
desc var=all /stat=default variance.
Mplus cannot read in character data, so any character variables in your dataset must either be converted to numeric or omitted. Looking at the variable view of our dataset,
we can see that all of our variables are numeric. For details on recoding variables, see our SPSS Data Management links.
Variable names in Mplus cannot exceed 8 characters. If your variable names exceed this length, they must be shortened. All of our variable names are 8 or fewer characters.
Before reading your data into Mplus, you must be familiar with whether or not your data contain missing values and, if they do, how those values are coded. In Mplus, you will need to explicitly list out the values that represent missing data. In our dataset, we can see that different variables have different values for missing. We can note which variables have which system missing values in SPSS: (.) for female, -9 for race, -99 for ses, -999 for schtyp, -9999 for read, and -99999 for write. Note that although missing values for female are shown with a dot (.) in the SPSS Data Editor, in the .csv file, they will be a blank.
Mplus can easily read comma separated data, so we can save our dataset as a .csv file. This can be done by choosing File, Save as, and then choosing "Comma delimited" from the "Save as type" drop down list. Also, we do not want the .csv file we create to include variable names, so we uncheck the "Write variable names to spreadsheet" box.
We can open the .csv file in Notepad or another text editor to see what our raw data looks like.
When reading in the data, we will refer Mplus to this file.
Instead of providing Mplus with a dataset containing variable names, you instead direct Mplus to a file without names and give the names within the Mplus code. To make this easier, we can save the variable names quickly from SPSS by copying them from the Variable View window and pasting them into a new text editor or directly into an Mplus input file.
We are now ready to read our data into Mplus. In the code below, we indicate the location of the .csv file we saved (NOTE: Mplus limits input lines to 80 characters, so a lengthy pathname may cause an error.) and indicate listwise deletion should be used in the analysis, just as we did in SPSS. We paste our list of variables in the Variable: block after Names are. In the next line, we indicate which values should be considered missing in each variable. Lastly, we indicate Type = basic in the Analysis: block so that the output includes summary statistics that allow us to check that the data was read in correctly. Below the code, we have printed some of the output that can be used to 1) make sure our missing values were correctly entered and 2) check the variable means.
Title: Entering data from .csv file Data: File is "D:/data/sample.csv"; Variable: Names are female race ses schtyp read write; Missing is female race (-9) ses (-99) schtyp (-999) read (-9999) write (-99999); Analysis: Type = basic; INPUT READING TERMINATED NORMALLY < ... output omitted ... > SUMMARY OF DATA Number of missing data patterns 7 SUMMARY OF MISSING DATA PATTERNS MISSING DATA PATTERNS (x = not missing) 1 2 3 4 5 6 7 FEMALE x x x x x x RACE x x x x x x SES x x x x x x SCHTYP x x x x x x READ x x x x x x WRITE x x x x x x MISSING DATA PATTERN FREQUENCIES Pattern Frequency Pattern Frequency Pattern Frequency 1 194 4 1 7 1 2 1 5 1 3 1 6 1 COVARIANCE COVERAGE OF DATA Minimum covariance coverage value 0.100 PROPORTION OF DATA PRESENT Covariance Coverage FEMALE RACE SES SCHTYP READ ________ ________ ________ ________ ________ FEMALE 0.995 RACE 0.990 0.995 SES 0.990 0.990 0.995 SCHTYP 0.990 0.990 0.990 0.995 READ 0.990 0.990 0.990 0.990 0.995 WRITE 0.990 0.990 0.990 0.990 0.990 Covariance Coverage WRITE ________ WRITE 0.995 RESULTS FOR BASIC ANALYSIS ESTIMATED SAMPLE STATISTICS Means FEMALE RACE SES SCHTYP READ ________ ________ ________ ________ ________ 1 0.542 3.411 2.056 1.161 52.259 Means WRITE ________ 1 52.811 Covariances FEMALE RACE SES SCHTYP READ ________ ________ ________ ________ ________ FEMALE 0.248 RACE 0.012 1.086 SES -0.042 0.148 0.524 SCHTYP 0.004 0.043 0.037 0.135 READ -0.236 2.453 2.139 0.326 104.190 WRITE 1.236 2.107 1.407 0.441 56.589 Covariances WRITE ________ WRITE 88.464 Correlations FEMALE RACE SES SCHTYP READ ________ ________ ________ ________ ________ FEMALE 1.000 RACE 0.024 1.000 SES -0.118 0.196 1.000 SCHTYP 0.020 0.112 0.139 1.000 READ -0.047 0.231 0.289 0.087 1.000 WRITE 0.264 0.215 0.207 0.128 0.589 Correlations WRITE ________ WRITE 1.000
We can compare these missing data patterns and means to our summaries from SPSS. In both datasets, we have 194 complete cases and our variable means match.
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