Learning Stata

Collecting stata commands that are very useful but not used frequently, namely, those I can not remember well. It will get very long ...
*This post was editted by * Maxico (a Markdown *based editor for * Evernote *) first, then copied here. * The Maxico version looks much better.

• V - Commands regarding Variables
• M - Macros, i.e., local and global
• F - Read, import, or export Files
• SSC - Commands from SSC
• F - Useful Functions

V

Variable Labels

Transfer a variable label to another

• Copy a variable label to a local
  • local lbl: variable label oldvar
  • Pass to another: label var newvar "`lbl'"
• An old version: _crcslbl newvar oldvar
  • This one only copies the variable label
• A new vewsion: copydesc oldvar newvar
  • This one copies the descriptive properties too

-- By Nicholas J. Cox

Copy variable labels before collapse

A systematic way to do this is with a foreach loop.

foreach v of var * {
  local l`v' : variable label `v'
    if `"`l`v''"' == "" {
        local l`v' "`v'"
        }
    }

Then after reshape check all variable labels and replace blanks by any saved labels:

foreach v of var * { 
    local L`v' : variable label `v' 
        if `"`L`v''"' == "" & `"`l`v''"' != "" { 
            label var `v' `"`l`v''"' 
    }
} 

-- By Nicholas J. Cox

M

Use of a global

• Defining a global is just as defining a local global gl, but accessing to it one has to put a $ in front of it, i.e., $gl
• When a global is used with a local, "{ }" must be used. For example, let local i be 6, and gl be "var", the code di "$gl`i'" will not return var6 but 6 instead. One has to type

di "${gl`i'}"

F

Import data from other sources (New in STATA 2013)

Import is a new command in State 13. It can import -excel- file directly. It also replace the insheet using command.

Import from Excel file

This needs some special notes because it is really a great update for STATA 13.0.

• Command: import excel using
  • cellrange([start]:[end]): There should be no blank after colon
  • firstrow should always be specified because it is neat! It does not have to be the first row in the sheet, but the first row in the range defined in the command. When firstrow has been specified, blanks will be removed for naming a variable, and will be kept for variable labels automatically.

Import from a delimited text file

• Command: import delim using: rowrange, colrange, nummericc are all useful

SSC commands

sec family; ssc hot

• unique: module to report number of unique values in variable(s)
• labutil: modules for managing value and variable labels
• tabout: module to export publication quality cross-tabulations

F

String Functions

destring

• It is a command actually, but more used to replace real().
• It is quite safe because string variables will not be transferred into numeric if destring detects any non-numeric records. Records of "." will be treated directly into missing values though. Neat!
• Use option ignore() to deal with the delimiter ``,''. Note this option can handle more than one arguments, e.g., ignore("," "N.A." " ").