From: Louise Hoffman <louise.hoffman_at_gmail.com>

Date: Sun, 02 Mar 2008 21:18:29 +0100

R-help_at_r-project.org mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Sun 02 Mar 2008 - 20:22:01 GMT

Date: Sun, 02 Mar 2008 21:18:29 +0100

I would like to make General Linear Model (GLM) for the following data set http://louise.hoffman.googlepages.com/fuel.csv

The code I have written is

fuelData<-read.table('fuel.csv',header=TRUE, sep=',')
n<-dim(fuelData)[1]

xOnes<- matrix(1,nrow=n,ncol=1)

x<-cbind(xOnes,fuelData[,3])

y<-fuelData[,4]

theta<-((t(x)%*%x)^(-1))%*%t(x)%*%y

which gives

> theta

[,1]

[1,] 215.8374077

[2,] 0.1083491

When I do it in Matlab I get theta to be
79.69

0.18

which is correct. ~79 is the crossing of the y-axis.

Have I perhaps written theta wrong? The formula for theta is (alpha,beta)^T = (x^T * x)^(-1) * x^T * Y

where ^T means transposed.

Can someone see where the mistake is?

Hugs,

Louise

R-help_at_r-project.org mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Sun 02 Mar 2008 - 20:22:01 GMT

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