Re: [R] Sweave, mle and curve

From: <Friedrich.Leisch_at_tuwien.ac.at>
Date: Mon 13 Feb 2006 - 22:43:07 EST

>>>>> On Mon, 13 Feb 2006 11:16:14 +0100, >>>>> Gran Brostrm (GB) wrote:

> I am trying to write a lesson on maximum likelihood with Sweave. I get
> a surprising result with the following code, lec4.Snw:

> \documentclass[a4paper,12pt]{article}
> \usepackage[latin1]{inputenc}

> \title{Maximum likelihood}

> \author{Gran Brostrm}

> \begin{document}

> \maketitle

> <<fig=TRUE>>=
> ## Simulate Y:
> n <- 25
> Y <- sum(rpois(n, lambda = 1))
> Y
> ## Define minusloglik:
> minusloglik <- function(theta) n * theta - Y * log(theta)
> curve(minusloglik, 0.2, 2, xlab = "theta")

> library(stats4)
> cat("Y is now ", Y, "\n")
> fit <- mle(minusloglik, start = list(theta = Y/n))
> summary(fit)
> @

> \end{document}

> In R, I get:

  >> Sweave("lec4.Snw")

> Writing to file lec4.tex
> Processing code chunks ...
> 1 : echo term verbatim eps pdf
> Y is now 27
> Y is now 24

> You can now run LaTeX on 'lec4.tex'
  >>

> and the latex document will have two different mle's, one in the
> figure, and another one from 'mle'. One uses Y = 27 and the other Y =
> 24!

> I can save the situation by moving "Y <- ..." to a separaye "code chunk".
> Does 'fig=TRUE' imply that the code chunk is run twice?

Yes, once to get all textual output, and then once for each graphics format requested.

Best,

-- 
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                        Friedrich Leisch 
Institut fr Statistik                     Tel: (+43 1) 58801 10715
Technische Universitt Wien                Fax: (+43 1) 58801 10798
Wiedner Hauptstrae 8-10/1071
A-1040 Wien, Austria             http://www.ci.tuwien.ac.at/~leisch

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Received on Mon Feb 13 22:54:58 2006

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