Commit b4d52d43 authored by amarell's avatar amarell

Correction module2/exo1/toy_document_en.Rmd

parent 8bea253a
......@@ -5,20 +5,19 @@ date: "25 juin 2018"
output: html_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```
# Asking the maths library
My computer tells me that $\pi$ is approximatively
## Asking the maths library
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**
## Buffon's needle
Applying the method of [Buffon's needle](https://en.wikipedia.org/wiki/Buffon%27s_needle_problem), we get the __approximation__
```{r}
set.seed(42)
......@@ -28,8 +27,8 @@ 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 $X∼U(0,1)$ and $Y∼U(0,1)$, then $P[X2+Y2≤1]=\pi/4$ (see [“Monte Carlo method” on Wikipedia](https://en.wikipedia.org/wiki/Monte_Carlo_method)). The following code uses this approach:
## 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 $P[X2+Y2\leq 1]= \pi/4$ (see ["Monte Carlo method" on Wikipedia](https://en.wikipedia.org/wiki/Monte_Carlo_method)). The following code uses this approach:
```{r}
set.seed(42)
......@@ -40,8 +39,9 @@ library(ggplot2)
ggplot(df, aes(x=X,y=Y,color=Accept)) + geom_point(alpha=.2) + coord_fixed() + theme_bw()
```
It is therefore 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 :
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)
```
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