diff --git a/module2/exo1/toy_document_en.Rmd b/module2/exo1/toy_document_en.Rmd index eb907c63e2cec03e7e7cbdc95d661a6ab65a2baa..d54411471d8c85ab106d1f54e4d292d1ac6c3fe5 100644 --- a/module2/exo1/toy_document_en.Rmd +++ b/module2/exo1/toy_document_en.Rmd @@ -5,7 +5,6 @@ date: "20/05/2021" output: html_document --- - ```{r setup, include=FALSE} knitr::opts_chunk$set(echo = TRUE) ``` @@ -15,7 +14,8 @@ My computer tells me that $\pi$ is *approximatively* ```{r} pi -``` +``` + ## Buffon's needle Applying the method of [Buffon's needle](https://en.wikipedia.org/wiki/Buffon%27s_needle_problem), we get the __approximation__ @@ -27,7 +27,6 @@ theta = pi/2*runif(N) 2/(mean(x+sin(theta)>1)) ``` - ## Using a surface fraction argument 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: @@ -38,10 +37,11 @@ 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) - ```