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st: shortcut for adjusted means |

Date |
Wed, 09 Jan 2008 19:47:00 +0100 |

Has "adjusted mean" a precise meaning for you? Or is it a generic expression, like "regression"? Also thanks to previous suggestions by Garry Anderson, Kabir Chabal, Nick Cox, Quang Nguyen, Austin Nichols, Valerie Orozco, Dimitris Pavlopoulos, Thomas Steichen, and Tom Trikalinos, I finally managed to translate into Stata an S-Plus script which is said to produce adjusted means, which I need to regress an institution-level variable on individual-level covariates. Any shortcut for producing the same results? Can I have the same from -adjust- and how? id=1...63 is the panel (institution) identifier; v* are the 15 variables with 354 individual observations which need to be adjusted; x* are more independent variables (with just one observation per panel, i.e. 63); xmean is a matrix of means for collapsed v* (i.e. obtained after -bysort id: gen ns =_N- and then -collapse v* ns, by(id)-); muz is a row of overall means for x*; dz is a matrix of centered x*; ysum is the cumulative sum of the squared values of ns; mux is a matrix of 63 rows (the same row of overall unadjusted means for the UNcollapsed v* is repeated 63 times); d is a matrix of the UNcollapsed v* centered at each panel's mean; d2 is a matrix of the UNcollapsed v* centered at the overall mean. matcorr x* v*, covariance matrix(vv) matselrc vv vzz, r(x*) c(x*) /* To tell the truth, the command doesn't support the use of abridged names.*/ matselrc vv vzxi, r(x*) c(v*) matrix mse = d'*d/(354-63) matrix vu = mse matrix msa = d2'*d2/(63-1) scalar cc = (nt - ysum/nt)/(63-1) matrix vxi = (msa-mse)/cc matrix r2 = inv(vzz)*vzxi matrix r1 = vxi - vzxi'*r2 matrix idd = I(15) forval i=1/63 { mat p=inv((r1+vu)/ns[`i'])*r1 mat q=r2*(idd-p) mat xtilde`i' = xmean*p +mux*(idd-p)+dz*q mat def row`i' = xtilde`i'[`i'..`i',.] mat def adj = nullmat(adj)\row`i' } Nicola * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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