Message/Author 


Hello, I'm using a covariance matrix as an input for a SEM (see model below) in MPlus. It is commonly (but not always) returning an error code of zero variance in some variances for a covariance matrix in which the variance is not 0. Any ideas on why this is occurring? VARIABLE: NAMES ARE Moisture N_Fix BareGnd Bryoph Lich Forbs Gram Shrubs; USEVARIABLES ARE Moisture N_Fix BareGnd Bryoph Lich Forbs Gram Shrubs; ANALYSIS: TYPE IS GENERAL; ITERATIONS = 1000; CONVERGENCE = 0.00005; MODEL: Forbs ON Moisture; Shrubs ON Moisture; Gram ON Moisture; Bryoph ON Shrubs Gram Forbs Moisture ; Lich ON Shrubs Gram Forbs Moisture Bryoph ; BareGnd ON Shrubs Gram Forbs Lich Bryoph ; N_Fix ON Bryoph Lich BareGnd; Forbs WITH Shrubs; Forbs WITH Gram; Gram WITH Shrubs; OUTPUT: STANDARDIZED MODINDICES(3.84); *** ERROR One or more variables have a variance of zero. Variable Variance **MOISTURE 0.010 N_FIX 0.000 BAREGND 0.001 BRYOPH 0.001 **LICH 0.000 FORBS 0.000 **GRAM 0.000 **SHRUBS 0.001 


You don't show the DATA command but I suspect you are not using the TYPE option to indicate that the data are in the form of a covariance matrix. See Example 13.1 and the DATA command. 


Sorry about not posting the Data commands. Here they are. I am using the following Data Commands. Are these sufficient? I am using a full covariance matrix. TITLE: SEM of Alex Fiord Lowland NFixation Data DATA: FILE IS "bin_1_491_obs.txt"; TYPE IS FULLCOV; NOBSERVATIONS = 491; VARIABLE: NAMES ARE Moisture N_Fix BareGnd Bryoph Lich Forbs Gram Shrubs; USEVARIABLES ARE Moisture N_Fix BareGnd Bryoph Lich Forbs Gram Shrubs; EXAMPLE of Covariance for Moisture and N_Fix Moisture N_Fix Moisture 0.000929777 0.008661346 N_Fix 0.008661346 0.010370599 ERROR MESSAGE *** ERROR One or more variables have a variance of zero. Variable Variance **MOISTURE 0.010 N_FIX 0.000 


Please send the data, output, and your license number to support@statmodel.com. 

Joe posted on Sunday, April 29, 2012  8:48 pm



Hi, I am trying to estimate a growth model so that the variance of the intercept is zero (I have already done i@0). In this case I am trying the following: DEFINE: t0=prfsbprfsb; t1=prfpm3sprfsb; t2=prfpm4sprfsb; t3=prfsmprfsb; t4=prfpm7sprfsb; t5=prfpm8sprfsb; t6=prfpm9sprfsb; t8=prfseprfsb; MODEL: i s  t0@0 t1@1 t2@2 t3@3 t4@4 t5@5 t6@6 t8@8; so that the score of each occasion has the first score subtracted from it. However I keep getting the following error message. *** ERROR One or more variables have a variance of zero. Check your data and format statement. VARIANCE = NOCHECK did not work either because the "ESTIMATED COVARIANCE MATRIX was NONINVERTIBLE." Thank you for your suggestions. Best, Joe 


Please send the output and your license number to support@statmodel.com. 

Back to top 