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### [Lapack] linear least square solutions from dgeqp3+dormqr+dtrtrs were di

 ```Dear lapack developer: I used clapck to solve a linear least square problem (Ax=b), but I found the solutions were different from SAS 9.1 and Matlab R2010a. Routine dgeqp3 was used for a *QR* Factorization with Column Pivoting, after removing dependent columns, the dormqr was used for Q'*y, finaly, dtrtrs for inv(R)*Q'*y. The routines I used are dgeqp3, dormqr and dtrtrs, and the design matrix A is rank-deficient. please find the attached files as the data, please help. A is a 324*61 matrix stored by columns, and b is a 324*1 vector stored by column. R code: A <- scan("A") b <- scan("b") A <- matrix(A,nrow=324,ncol=61) b <- matrix(b,nrow=324,ncol=1) tol <- 1e-8 m <- nrow(A) n <- ncol(A) qrA <- qr(A,LAPACK=TRUE) jpvt <- qrA\$pivot R <- qr.R(qrA) Q <- qr.Q(qrA) p <- sum(abs(diag(R))>tol) R <- R[1:p,1:p] Q <- Q[,1:p] jpvt <- jpvt[1:p] x <- rep(0,n) x[jpvt] <- solve(R, t(Q)%*%b) -- ??? He Jianbo -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.eecs.utk.edu/mailman/private/lapack/attachments/20101107/0a0d5c8b/attachment-0001.html -------------- next part -------------- A non-text attachment was scrubbed... Name: A Type: application/octet-stream Size: 41363 bytes Desc: not available Url : http://lists.eecs.utk.edu/mailman/private/lapack/attachments/20101107/0a0d5c8b/A-0001.obj -------------- next part -------------- A non-text attachment was scrubbed... Name: b Type: application/octet-stream Size: 2003 bytes Desc: not available Url : http://lists.eecs.utk.edu/mailman/private/lapack/attachments/20101107/0a0d5c8b/b-0001.obj ```
 Current Thread [Lapack] linear least square solutions from dgeqp3+dormqr+dtrtrs were different from SAS/Matlab, He Jianbo <=

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