From: yangleicq <yanglei_cq_at_126.com>

Date: Wed, 25 Apr 2012 23:00:21 -0700 (PDT)

[10,] 5.14 1.7

*> n=10
*

*> p=2
*

*> y <- c(4.81,4.17,4.41,3.59,5.87,3.83,6.03,4.89,4.32,4.69)
*

*> ny=1L
*

*> tol=1e-07
*

*> coefficients=double(p)
*

*> residuals=double(n)
*

*> effects=double(n)
*

*> rank=integer(1L)
*

*> pivot=1:n
*

*> qraux=double(n)
*

*> work=double(2*n)
*

*>
*

*>
*

*>
*

> fittt<-.Fortran("dqrls", qr =qr, n = n,

*>
*

> fittt$coefficients

[1] 0 0

Date: Wed, 25 Apr 2012 23:00:21 -0700 (PDT)

ink1">Hi, all.

I want to write some functions like glm() so i studied it.
In glm.fit(), it calls a fortran subroutine named "dqrfit" to compute least
ink2">squares solutions

to the system

To learn how "dqrfit" works, I just follow how glm() calls "dqrfit" by my own example, my codes are given below:

*> qr <-
*

> matrix(c(4.17,5.58,5.18,6.11,4.50,4.61,5.17,4.53,5.33,5.14,2.3,1.7,1.3,1.7,1.7,1.6,1,1.7,1.7,1.7),ncol=2)

*> qr
*

[1,] 4.17 2.3 [2,] 5.58 1.7 [3,] 5.18 1.3 [4,] 6.11 1.7 [5,] 4.50 1.7 [6,] 4.61 1.6 [7,] 5.17 1.0 [8,] 4.53 1.7 [9,] 5.33 1.7

[10,] 5.14 1.7

> fittt<-.Fortran("dqrls", qr =qr, n = n,

+ p = p, y = y, ny = ny, tol = tol, coefficients=coefficients, + residuals = residuals, effects = effects, + rank = rank, pivot = pivot, qraux = qraux, + work = work, PACKAGE = "base")

> fittt$coefficients

[1] 0 0

but when i use lm() which also calls "dqrls" internally to fit this model, it gives reasonable result.

(Intercept) qr1 qr2 11.1766 -0.8833 -1.2628

when I change the coefficients to be c(1,1), the output from "dqrls", fittt$coefficients also equals to c(1,1). That means the .Fortran("dqrls", qr=qr,n=n,p=p,...) did nothing to the coefficients! I don't know why, is there anything I did wrong or missed? How can I get the result from "dqrls" as what lm() or glm() gets from "dqrls"?

Thanks in advance. Best Regards.

-- View this message in context: http://r.789695.n4.nabble.com/How-does-Fortran-dqrls-work-tp4588973p4588973.html Sent from the R devel mailing list archive at Nabble.com. ______________________________________________ R-devel_at_r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-develReceived on Thu 26 Apr 2012 - 11:19:54 GMT

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