example of permutation r

permutation.qmd

---
title: "Permutation"
author: "Julie Gravier"
date: "01/01/2023"
format: 
  html:
    fig-width: 8
    fig-height: 4
    code-fold: false
---

# First element with basic
Creating a vector of length 10
```{r}
vec <- seq(1,10,1)
vec
```

We want to permute elements with a probability (proba is relative to the number of element).
Example with prob = 0.2

```{r}
proba <- 0.2
vecsamp <- sample(x = vec, size = length(vec)*proba, replace = F)
vecsamp

# second sampling with same proba, but on initial vector vec without the result of vecsamp
vec2 <- setdiff(x = vec, y = vecsamp) # element of x not in y
vec2
# resampling:
vecsamp2 <- sample(x = vec2, size = length(vec)*proba, replace = F)
vecsamp2
```

Permutation of the first vector _vec_ with the results of samplings>
```{r}
finalvec <- vec

for (i in 1:length(vec)) {
  # is vec[i] is equal to vecsamp[i] ? then replace
  for (j in 1:length(vecsamp)) {
  
   if (vec[i] == vecsamp[j]) {
      finalvec[i] <- vecsamp2[j]
   } else if (vec[i] == vecsamp2[j]) {
      finalvec[i] <- vecsamp[j]
   }
    
  }
  
}

vec
finalvec

```