Listing data and basic command syntax

1 10 Listing data and basic command syntaxCommand syntaxThis chapter gives a basic lesson on Stata s command syntax while showing how to control theappearance of a data we have seen throughout this manual, you have a choice between using menus and dialogsand using the command window. Although many find the menus more natural and the Commandwindow baffling at first, some practice makes working with the command window often much fasterthan using menus and dialogs. The command window can become a faster way of working becauseof the clean and regular syntax of Stata commands. We will cover enough to get you started;helplanguagehas more information and examples, and[U] 11 Language syntaxhas all the syntax for thelistcommand can be seen by typinghelp list:list[varlist][if][in][,options]Here is how to read this syntax : Anything inside square brackets is optional. For thelistcommand, optional.

2 Avarlistis a list of variable optional. Theifqualifier restricts the command to run only on those observations forwhich the qualifier is true. We saw examples of this in[GSW] 6 Using the Data optional. Theinqualifier restricts the command to run on particular ,andoptionsare separated from the rest of the command by acomma. Optional pieces do not preclude one another unless explicitly stated. For thelistcommand,it is possible to use avarlistwithifandin. If a part of a word is underlined, the underlined part is the minimum abbreviation. Anyabbreviation at least this long is Thelinlistis underlined, sol,li, andlisare all equivalent tolist. Anything not inside square brackets is required. For thelistcommand, only the commanditself is these rules in mind, let s investigate howlistbehaves when called with different will be using the the end of the previous with a variable listVariable lists (orvarlists) can be specified in a variety of ways, all designed to save typing andencourage good variable names.

3 Thevarlistis optional forlist. This means that if no variables are specified, it is equivalent tospecifying all variables. Another way to think of it is that the default behavior of the commandis to run on all variables unless restricted by avarlist. You can list a subset of variables explicitly, as inlist make mpg price. There are also many shorthand notations:m*means all variables starting all variables frompricethroughweightin the dataset all variables starting withma, followed by any character, and ending [ GSW ] 10 Listing data and basic command syntax You can list a variable by using an abbreviation unique to that variable, as inlist gearr~ the abbreviation is not unique, Stata returns an error message.. listmake price mpg weight gear_r~o Rabbit 4697 25 1930 98 8814 21 4060

4 monza 3667 . 2750 22 2930 510 5079 24 2280 Regal

5 5189 20 3280 810 8129 . 2750 foreign. l make mpg pricemake mpg Rabbit 25 98 21 monza .

6 510 24 Regal 20 810 . 8129. list m*make Rabbit 98 monza . 510 Regal 810.

7 Li price-weightprice mpg 25 21 . 22 24 20.

8 2750 [ GSW ] 10 Listing data and basic command syntax 3 . list ma? 810. l gear_r~ogear_r~ list with ifTheifqualifier uses a logical expression to determine which observations to use. If the expressionis true, the observation is used in the command ; otherwise, it is skipped. The operators whose resultsare either true or false are<less than<=less than or equal==equal>greater than>=greater than or equal!=not equal&and|or!not (logical negation;~can also be used)()parentheses are for grouping to specify order of evaluationIn the logical expressions,&is evaluated before|(similar to multiplication before addition inarithmetic). You can use this in your expressions, but it is often better to use parentheses to ensurethat the expressions are evaluated in the proper order.

9 See[U] Operatorsfor complete [ GSW ] 10 Listing data and basic command syntax . listmake price mpg weight gear_r~o Rabbit 4697 25 1930 98 8814 21 4060

10 monza 3667 . 2750 22 2930 510 5079 24 2280 Regal