{smcl}
{* 2sep2009}{...}
{cmd: help elemlist}
{hline}

{title:Title} 

{pstd}{cmd:element lists (generalized varlists)}

{title:Description}

{pstd}An {it:elemlist} is a superset of a Stata {varlist}. You can just treat it as a {varlist} and go. Or, read on for the details. The main distinction is that the {it:elemlist} allows more, and more flexible, ways to specify ranges.

{pstd}Secondarily, an {it:elemlist} can include {bf:modifiers}, described below, and is used in some places to select things other than variables.

{pstd}Abbreviations and wildcards ({cmd:*}, {cmd:?}, and {cmd:~}) work as in a {varlist}.

{title:Ranges}

{phang}>>> For the following examples, first {stata sysuse elemlist.dta}. The dataset contains the variables: {bf:a b ba c x y ya yb z}.

{pstd}Ranges can be specified in two distinct ways. First, similarly to a {varlist},  as all items between two endpoints. For example:

{pmore}{stata tlist a-z}

{pstd}However, the endpoints can be listed in either order:

{pmore}{stata tlist z-a}

{pstd}And the indivdual terms can include wildcards. When a wildcard is included, the most extreme member(s) of the specfied set are used as the endpoint(s):

{pmore}{stata tlist b*-y?}

{pstd}The second way to specify a range is as {bf:extensions} around one or more anchor items. The syntax would be:

{pmore}{it:anchor}[{it:ext1}][{it:ext2}]

{pstd}where {it:anchor} can include wildcards, and {it:ext1} and {it:ext2} are of the form

{pmore}{{cmd:<}|{cmd:>}}{it:#}

{pstd}where {it:#} indicates how many elements before ({cmd:<}) and/or after ({cmd:>}) the {it:anchor} to include. For example:

{p2colset 9 25 25 2}
{p2col:{stata tlist c>1}}specifies {cmd:c} and the variable after {cmd:c}.

{p2col:{stata tlist x>2<2}}specifies all variables within 2 of {cmd:x}. 

{p2col:{stata tlist a>3>6}}specifies the variables from 3 to 6 after {cmd:a}.

{p2col:{stata tlist *b>1}}specfies all variables ending with {cmd:b}, and for each of those, the following variable.

{title:Modifiers}

{pstd}Some commands will allow an {it:elemlist} to include specific {bf:modifiers}. In general, a {bf:modifier} is just a dot ({cmd:.}) followed (perhaps) by some text, which goes at the end of any term. For example:

{pmore}{cmd:a.mod1}{p_end}
{pmore}{cmd:b*.mod2}{p_end}
{pmore}{cmd:a-z.}{p_end}
{pmore}{cmd:c>1<1.mod4}{p_end}

{pstd}The modifier affects how all the items specified in that term will be treated by the current command. For example, 

{phang2}{cmd:. bivar z b*.cat} would treat all variables starting with {cmd:b} as categorical variables.

{phang2}{cmd:. t a y-z.} would collapse all non-missing values of variables {cmd:y} through {cmd:z}.

{pstd}The allowable modifiers, as well as their effects, are specific to each command.