Stata Programming Cheat Sheet

Stata Programming Cheat Sheet

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  Programming Cheat Sheetwith Stata14.1 For more info see Stata’s reference manual (stata.com) Tim Essam (tessam@usaid.gov) • Laura Hughes (lhughes@usaid.gov) follow us @StataRGIS and @flaneuseks inspired by RStudio’s awesome Cheat Sheets (rstudio.com/resources/cheatsheets) updated June 2016 CC BY 4.0 geocenter.github.io/StataTraining Disclaimer: we are not affiliated with Stata. But we like it. PUTTING IT ALL TOGETHER sysuse auto, clear generate car_make = word(make, 1) levelsof car_make, local(cmake) local i = 1 local cmake_len : word count `cmake' foreach x of local cmake { display in yellow "Make group `i' is `x'" if `i' == `cmake_len' { display "The total number of groups is `i'" } local i = `++i' } define the local i to be an iterator tests the position of the iterator, executes contents in brackets when the condition is true increment iterator by one store the length of local cmake in local cmake_len calculate unique groups of car_make and store in local cmake pull out the first word from the make variable see also capture and scalar _rc Stata has three options for repeating commands over lists or values: foreach, forvalues, and while. Though each has a different first line, the syntax is consistent: Loops: Automate Repetitive Tasks ANATOMY OF A LOOP see also while i = 10(10)50 10, 20, 30, ... i = 10 20 to 50 10, 20, 30, ... i = 10/50 10, 11, 12, ... ITERATORS DEBUGGING CODE set trace on (off) trace the execution of programs for error checking foreach x of varlist var1 var2 var3 { command `x', option } open brace must appear on first line temporary variable used only within the loop objects to repeat over close brace must appear on final line by itself command(s) you want to repeat can be one line or many ... requires local macro notation FOREACH: REPEAT COMMANDS OVER STRINGS, LISTS, OR VARIABLES FORVALUES: REPEAT COMMANDS OVER LISTS OF NUMBERS display 10 display 20 ... display length("Dr. Nick") display length("Dr. Hibbert") When calling a command that takes a string, surround the macro name with quotes. foreach x in "Dr. Nick" "Dr. Hibbert" { display length ( "` x '" ) } LISTS sysuse "auto.dta", clear tab rep78, missing sysuse "auto2.dta", clear tab rep78, missing same as... loops repeat the same command over different arguments: foreach x in auto.dta auto2.dta { sysuse "`x'", clear tab rep78, missing } STRINGS summarize mpg summarize weight • foreach in takes any list as an argument with elements separated by spaces • foreach of requires you to state the list type, which makes it faster foreach x in mpg weight { summarize `x' } foreach x of varlist mpg weight { summarize `x' } must define list type VARIABLES Use display command to show the iterator value at each step in the loop foreach x in|of [ local, global, varlist, newlist, numlist ] { Stata commands referring to `x' } list types: objects over which the commands will be repeated forvalues i = 10(10)50 { display `i' } numeric values over which loop will run iterator Additional Programming Resources install a package from a Github repository net install package, from (https://raw.githubusercontent.com/username/repo/master) download all examples from this cheat sheet in a .do file bit.ly/statacode https://github.com/andrewheiss/SublimeStataEnhanced configure Sublime text for Stata 11-14 adolist List/copy user-written .ado files adoupdate Update user-written .ado files ssc install adolist The estout and outreg2 packages provide numerous, flexible options for making tables after estimation commands. See also putexcel command. EXPORTING RESULTS esttab using “auto_reg.txt”, replace plain se export summary table to a text file, include standard errors outreg2 [est1 est2] using “auto_reg2.txt”, see replace export summary table to a text file using outreg2 syntax esttab est1 est2, se star(* 0.10 ** 0.05 *** 0.01) label create summary table with standard errors and labels Access & Save Stored r- and e-class Objects4 mean price returns list of scalars, macros, matrices and functions summarize price, detail returns a list of scalars return list ereturn lister Many Stata commands store results in types of lists. To access these, use return or ereturn commands. Stored results can be scalars, macros, matrices or functions. create a temporary copy of active dataframepreserve restore temporary copy to original pointrestore create a new variable equal to average of price generate p_mean = r(mean) scalars: e(df_r) = 73 e(N_over) = 1 e(k_eq) = 1 e(rank) = 1 e(N) = 73 scalars: ... r(N) = 74 r(sd) = 2949.49... r(mean) = 6165.25... r(Var) = 86995225.97... create a new variable equal to obs. in estimation command generate meanN = e(N) Results are replaced each time an r-class / e-class command is called set restore points to test code that changes data create local variable called myLocal with the strings price mpg and length local myLocal price mpg length levelsof rep78, local(levels) create a sorted list of distinct values of rep78, store results in a local macro called levels summarize ` myLocal ' summarize contents of local myLocal add a ` before and a ' after local macro name to call PRIVATEavailable only in programs, loops, or .do filesLOCALS local varLab: variable label foreign store the variable label for foreign in the local varLab can also do with value labels tempfile myAuto save `myAuto' create a temporary file to be used within a program tempvar temp1 generate `temp1' = mpg^2 summarize `temp1' initialize a new temporary variable called temp1 summarize the temporary variable temp1 save squared mpg values in temp1 special locals for loops/programsTEMPVARS & TEMPFILES Macros3 public or private variables storing text global pathdata "C:/Users/SantasLittleHelper/Stata" define a global variable called pathdata available through Stata sessions PUBLICGLOBALS global myGlobal price mpg length summarize $myGlobal summarize price mpg length using global cd $pathdata change working directory by calling global macro add a $ before calling a global macro see also tempname matselrc b x, c(1 3) select columns 1 & 3 of matrix b & store in new matrix x findit matselrc mat2txt, matrix(ad1) saving(textfile.txt) replace ssc install mat2txtexport a matrix to a text file Matrices2 e-class results are stored as matrices matrix ad1 = a d row bind matrices matrix ad2 = a , d column bind matrices matrix a = (4 5 6) create a 3 x 1 matrix matrix b = (7, 8, 9) create a 1 x 3 matrix matrix d = b' transpose matrix b; store in d scalar a1 = “I am a string scalar” create a scalar a1 storing a string Scalars1 both r- and e-class results contain scalars scalar x1 = 3 create a scalar x1 storing the number 3 Scalars can hold numeric values or arbitrarily long strings DISPLAYING & DELETING BUILDING BLOCKS [scalar | matrix | macro | estimates] [list | drop] b list contents of object b or drop (delete) object b [scalar | matrix | macro | estimates] dir list all defined objects for that class list contents of matrix b matrix list b list all matrices matrix dir delete scalar x1 scalar drop x1 Use estimates store to compile results for later use estimates table est1 est2 est3 print a table of the two estimation results est1 and est2 estimates store est1 store previous estimation results est1 in memory regress price weight eststo est2: regress price weight mpg eststo est3: regress price weight mpg foreign estimate two regression models and store estimation results ssc install estout ACCESSING ESTIMATION RESULTS After you run any estimation command, the results of the estimates are stored in a structure that you can save, view, compare, and export basic components of programming 2 rectangular array of quantities or expressions 3 pointers that store text (global or local) 1 MATRICES MACROS SCALARS individual numbers or strings R- AND E-CLASS:Stata stores calculation results in two* main classes: r ereturn results from general commands such as summary or tabulate return results from estimation commands such as regress or mean To assign values to individual variables use: e e r Building Blocks * there’s also s- and n-class