[R] fitted values are different from manually calculating

[Dimitris Rizopoulos]

why do you say this? Check for instance the following code:

x1 <- runif(100, -5, 5)
x2 <- rnorm(100)
x3 <- rep(0:1, each = 50)
y <- 2 + 0.5 * x1 + 2 * x2 - 3 * x3 + rnorm(100)

fit <- lm(y ~ x1 + x2 + x3)

all.equal(
    as.vector(fitted(fit)),
    as.vector(model.matrix(fit) %*% coef(fit))
)


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: <gatemaze at gmail.com>
To: <r-help at stat.math.ethz.ch>
Sent: Tuesday, February 19, 2008 3:41 PM
Subject: [R] fitted values are different from manually calculating


> Hello,
>
> on a simple linear model the values produced from the fitted(model) 
> function
> are difference from manually calculating on calc. Will anyone have a 
> clue...
> or any insights on how fitted function calculates the values? Thank 
> you.
>
> -- 
> -- Yianni
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
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> and provide commented, minimal, self-contained, reproducible code.
> 


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