国外大学讲义：Stata Programing（stata编程）.pptVIP

H.S. * H.S. * Stata 8, Programing Hein Stigum Presentation, data and programs at: http://folk.uio.no/heins/ * H.S. * Programing Programing examples Get and use results from commands Automate tasks Define functions Define new commands Two languages Stata Macro language For small problems Mata For large problem * H.S. * Stata Macro Language * H.S. * Scalar Scalar (numbers) scalar a=2 define display a display content gen x2=a*x use Will not work in plots Only numbers * H.S. * Macro Local Macro (number or string) local a=2 define display `a’ display content gen x2=`a’*x use Global Macro (number or string) global a=2 define display $a display content gen x$a=x^2 use Global has a “longer life” than local * H.S. * Matrix Matrix (matrix of numbers) matrix A=J(2,3,0) define 2*3 matrix of 0’s matrix list A display content matrix A[2,1]=12 change element matrix rownames A=mean1 mean2 set names matrix colnames A=low med high set names Only numbers No vectors * H.S. * Use returned results Run command: Look for returned results: Use returned results: global m=r(mean) Or put in macro: * H.S. * Example: Density plot with extra info * H.S. * Commands for previous plot Run command: Put in macro: Use macros: summarize weight, detail global N=r(N) Number of observations global p10=r(p10) 10-th percentile global p50=r(p50) global p90=r(p90) twoway (kdensity weight) , note(N=$N) xlabel(minmax $p10 $p50 $p90, format(%5.0f)) * H.S. * Get regression results Run regression: Put in matrices: Use macros: logistic lbw sex age matrix b=e(b) vector of coefficients, constant last matrix V=e(V) variance-covariance matrix Alternative: global b1= _b[sex] sex-coefficient global se1=_se[sex] sex-standard error matrix var=vecdiag(e(V)) variance global ci1=exp(b[1,1]-1.96*sqrt(var[1,1])) lower CI for sex Look for returned results: ereturn list * H.S. * Loops Over variables Over index (for-loop) foreach var of varlist sex mage gest { summarize