Matrix multiplications
Roy, Yes, t(y-X %*% b) is the transpose of y-X %*% b. In principle the product of t(y-X %*% b) *(y-X %*% b) is a scalar, I don't know why I have an error message after the following line: (t(y-X %*% b)%*%(y-X %*% b)/(length(y)-ncol(X)))*solve(t(X)%*% X) Thanks On Sat, May 21, 2016 at 9:10 PM, Roy Mendelssohn - NOAA Federal <
roy.mendelssohn at noaa.gov> wrote:
str(t(y-X %*% b))
num [1, 1:10] 0.595 -1.7538 -0.0498 -1.651 -0.6328 ...
str((y-X %*% b))
num [1:10, 1] 0.595 -1.7538 -0.0498 -1.651 -0.6328 ? -Roy
On May 21, 2016, at 12:00 PM, george brida <george.brida at gmail.com>
wrote:
Dear R users: I have written the following lines :
x=c(10,11,12,13,14,17,15,16,10,11,41,25,26,14,12,14,15,20,14,22) x=matrix(x,ncol=2) a=matrix(1,nrow(x),1) X=cbind(a,x) y=c(12.00, 11.00, 13.00, 12.50, 14.00, 18.50, 15.00, 12.50, 13.75,
15.00)
b=solve(t(X)%*% X)%*% t(X)%*% y
when I wrote the following line
(t(y-X %*% b)%*%(y-X %*% b)/(length(y)-ncol(X)))*solve(t(X)%*% X)
I have obtained an error message, I don't know why namely (t(y-X %*% b)%*%(y-X %*% b)/(length(y)-ncol(X))) is a scalar:
(t(y-X %*% b)%*%(y-X %*% b)/(length(y)-ncol(X)))
[,1]
[1,] 3.620354
Can you please help me.
Thank you
George
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http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. ********************** "The contents of this message do not reflect any position of the U.S. Government or NOAA." ********************** Roy Mendelssohn Supervisory Operations Research Analyst NOAA/NMFS Environmental Research Division Southwest Fisheries Science Center ***Note new address and phone*** 110 Shaffer Road Santa Cruz, CA 95060 Phone: (831)-420-3666 Fax: (831) 420-3980 e-mail: Roy.Mendelssohn at noaa.gov www: http://www.pfeg.noaa.gov/ "Old age and treachery will overcome youth and skill." "From those who have been given much, much will be expected" "the arc of the moral universe is long, but it bends toward justice" -MLK Jr.