.- help for ^eq^ .- Define and list equations ------------------------- ^eq^ [^define^] eqtn ^eq^ [^define^] eqname ^:^ [eqtn] ^eq dir^ [^_all^ | eqname [eqname ..]] ^eq list^ [^_all^ | eqname [eqname ..]] ^eq drop^ {^_all^ | eqname [eqname ..]} Description ----------- ^eq define^ is used to define equations in ^gllamm^. In Stata 5 and earlier this was also used by Stata's own multivariate estimation commands. The command continues to work in Stata 8 but is no longer documented. ^eq dir^ and ^eq list^ are used to review equations that have been defined. ^eq drop^ is used to eliminate previously defined equations. ^gllamm^ has options ^eqs(eqnames)^ ^geqs(eqnames)^ ^peqs(eqname)^ and ^s(eqname)^ where eqnames is a list of equation names and eqname is an equation name. You first define equations using ^eq^ and then estimate the model. Equations are named and usually define a variable list. For instance, to estimate a factor model in ^gllamm^, an equation of the following kind must be defined: . ^eq load: d1 d2 d3^ where d1, d2 and d3 are dummy variables for three variables or items loading on one of the factors. You can abbreviate variable names and take all the other shortcuts you would when specifying a varlist in a command: . ^eq load: d1-d3^ When you do not specify the equation name followed by a colon, the first name is taken both as the equation name and as part of the contents of the equation. There is one exception to this rule. You may not type . ^eq price^ You must type instead . ^eq price: price^ (Such nearly empty equations are not silly; it could mean that price is to be estimated by an intercept-only equation.) One can also define completely empty equations in this way: . ^eq price: ^ Note the distinction: "^eq price: price^" defines equation price to contain "price"; "^eq price:^" defines price to contain nothing. Equations can be dropped, . ^eq drop load^ . ^eq load: d1 d2 d3^ or you can redefine equations without bothering to drop them first. Equations may be listed for review: . ^eq list load^ . ^eq list load1 load2^ . ^eq list^ You can list just the equation names using ^eq dir^: . ^eq dir^