From 691378010fc877bed8038951f6b3810d5bd582c3 Mon Sep 17 00:00:00 2001 From: 3582521b868d7c148df1de482ec5a734 <3582521b868d7c148df1de482ec5a734@app-learninglab.inria.fr> Date: Wed, 25 Oct 2023 21:07:59 +0000 Subject: [PATCH] Update toy_document_en.Rmd --- module2/exo1/toy_document_en.Rmd | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/module2/exo1/toy_document_en.Rmd b/module2/exo1/toy_document_en.Rmd index 3015191..8ca3190 100644 --- a/module2/exo1/toy_document_en.Rmd +++ b/module2/exo1/toy_document_en.Rmd @@ -17,7 +17,7 @@ My computer tells me that $\pi$ is *approximatively* pi ``` -## Buffon's needle +## Buffon's needle Applying the method of [Buffon's needle](https://en.wikipedia.org/wiki/Buffon%27s_needle_problem), we get the __approximation__ @@ -34,16 +34,17 @@ theta = pi/2*runif(N) A method that is easier to understand and does not make use of the $\sin$ function is based on the fact that if $X\sim U(0,1)$ and $Y\sim U(0,1)$, then $P[X^2+Y^2\leq 1] = \pi/4$ (see ["Monte Carlo method" on Wikipedia](https://en.wikipedia.org/wiki/Monte_Carlo_method)). The following code uses this approach: ```{r} -set.seed(42) -N = 1000 -df = data.frame(X = runif(N), Y = runif(N)) -df$Accept = (df$X**2 + df$Y**2 <=1) -library(ggplot2) +set.seed(42) +N = 1000 +df = data.frame(X = runif(N), Y = runif(N)) +df$Accept = (df$X**2 + df$Y**2 <=1) +library(ggplot2) ggplot(df, aes(x=X,y=Y,color=Accept)) + geom_point(alpha=.2) + coord_fixed() + theme_bw() + ``` It is then straightforward to obtain a (not really good) approximation to $\pi$ by counting how many times, on average, $X^2 + Y^2$ is smaller than 1: -```{r} -4*mean(df$Accept) -``` +```{r} +4*mean(df$Accept) +``` \ No newline at end of file -- 2.18.1