大学讲义：Stata Programing（stata编程）

1、Feb-22H.S.1Stata 8, ProgramingHein StigumPresentation, data and programs at: :/folk.uio.no/heins/Feb-22H.S.2Programing Programing examples Get and use results from commands Automate tasks Define functions Define new commands Two languages Stata Macro languageFor small problems MataFor large problemF

2、eb-22H.S.3Stata Macro LanguageFeb-22H.S.4Scalar Scalar (numbers)scalar a=2definedisplay adisplay contentgen x2=a*xuse Will not work in plots Only numbersFeb-22H.S.5Macro Local Macro (number or string)local a=2definedisplay adisplay contentgen x2=a*xuse Global Macro (number or string)global a=2define

3、display $adisplay contentgen x$a=x2use Global has a “longer life” than localFeb-22H.S.6Matrix Matrix (matrix of numbers)matrix A=J(2,3,0)define 2*3 matrix of 0smatrix list Adisplay contentmatrix A2,1=12change elementmatrix rownames A=mean1 mean2set namesmatrix colnames A=low med highset namesOnly nu

4、mbersNo vectorsFeb-22H.S.7Use returned resultsRun command:Look for returned results:Use returned results:global m=r(mean)Or put in macro:Feb-22H.S.8minw25%50%75%wmax200318039405350204036005080WeightN=5832005350282036004280BirthweightN=583Example: Density plot with extra infoFeb-22H.S.9Commands for p

5、revious plotRun command:Put in macro:Use macros:summarize weight, detailglobal N=r(N)Number of observationsglobal p10=r(p10)10-th percentileglobal p50=r(p50)global p90=r(p90)twoway (kdensity weight) , note(N=$N) xlabel(minmax $p10 $p50 $p90, format(%5.0f) Feb-22H.S.10Get regression resultsRun regres

6、sion:Put in matrices:Use macros:logistic lbw sex agematrix b=e(b)vector of coefficients, constant lastmatrix V=e(V)variance-covariance matrixAlternative:global b1= _bsexsex-coefficientglobal se1=_sesexsex-standard errormatrix var=vecdiag(e(V)varianceglobal ci1=exp(b1,1-1.96*sqrt(var1,1) lower CI for

7、 sexLook for returned results:ereturn listFeb-22H.S.11Loops Over variables Over index (for-loop)foreach var of varlist sex mage gest summarize varforvalues i=1(1) 5 display iFeb-22H.S.12Loops example: Crude ORs Version 1 Version 2, collect results in a matrixforeach var of varlist sex mage gest logi

8、stic lbw varmatrix A=J(3,3,0) local i=1foreach var of varlist sex mage gest logistic lbw varmatrix Ai,1=exp(_bvar)local +iFeb-22H.S.13MataFeb-22H.S.14Mata commands Start and stop matastart Mata endstop Mata Help help mata help m4 introlist of functions help mata max()given functionMata commands cont

9、. Vectorx=(1,2,3)line vectory=(456)column vector x; y; y1display x and y and y1z=x+yx+y-transposedx:+1element by elementDifferences from macro language:Feb-22H.S.15Mata commands cont. MatrixA=J(2,3,0)2 by 3 matrix of 0sA1,2=14change elementA1,.1. lineA.,11. columnA(13),(1,2)submatrix: line 1 and 3,

10、col 1 and 2Strong syntax, direct access to all submatrices Feb-22H.S.16Mata read and set Read or setA=st_matrix(r(V) 1. read from Statast_matrix(X,A)2. set or reset in Statas=st_matrixrowstripe(r(V)row namesm=st_global(”m)global macrost_addvar(double,(“y, “x”)add variablesst_store(1,n),(“y, “x”),(y1

11、,x1)store valuesFeb-22H.S.17whereStatanameMatanameMata commands cont. Run Stata commandsstata(”cmd”) run Stata commandsstata(”mean x”+strofreal(i) mean x1stata(”mean x”+strofreal(i)+”,detail”) mean x1, detailRemember spaces!Feb-22H.S.18Feb-22H.S.19Example: plot regression results Ideacoeff and se as

12、 vectors, calculate CIstore vectors as data Plotscatter and rcap Plot elements_y1-4_pointOR or coeff_lowCI_highCIparitygest10magesex-4-3-2-101234Estimates with 95% confidence intervalN=536 constant=20.77281Logistic regression on lbwFeb-22H.S.20Example: plot valid and missing Ideatabstat, stat(N)missing relative to 1. store vectors as data Plotbar, rbar, scatter with mlabel Plot elements_