# Clase del 30 agosto 2022 ###### tags: `Curso IPE 2022` ## Objetivos - Muestreo aleatorio y cálculo de frecuencia. - Graficar un histograma. ## Funcionalidades - Saber usar la funcion `sample` con y sin reposición. - Comando `table`. - Comando `barplot`. ## Ejercicio 1 Consideramos el ejercicio 11 del practico 1: > De cuantas maneras se pueden ordenar 5 libros en una fila? Llamemosle "A", "B", "C", "D", "E" a los libros. ```R x <- c("A", "B", "C", "D", "E") x <- LETTERS[1:5] > sample(x, 5, replace = FALSE) [1] "C" "E" "A" "D" "B" > sample(x, 5, replace = FALSE) [1] "C" "E" "B" "D" "A" > sample(x, 5, replace = FALSE) [1] "D" "C" "A" "B" "E" > sample(x, 5, replace = FALSE) [1] "A" "E" "C" "B" "D" > sample(x, 5, replace = FALSE) [1] "D" "E" "B" "C" "A" ``` ## Permutaciones - https://www.r-bloggers.com/2020/09/permutations-in-r/ - https://stackoverflow.com/questions/22569176/how-to-generate-permutations-or-combinations-of-object-in-r/47983855#47983855 ### Para instalar ```R > install.packages("combinat") ``` ```R > install.packages("combinat") trying URL 'https://cran.rstudio.com/bin/macosx/contrib/4.2/combinat_0.0-8.tgz' Content type 'application/x-gzip' length 40732 bytes (39 KB) ================================================== downloaded 39 KB The downloaded binary packages are in /var/folders/0p/w0s_xyq10178j9qhlz_0h90m0000gp/T//Rtmp5XfM1H/downloaded_packages ``` ### Para utilizar ```R > library(combinat) ``` ```R > permn(1:3) [[1]] [1] 1 2 3 [[2]] [1] 1 3 2 [[3]] [1] 3 1 2 [[4]] [1] 3 2 1 [[5]] [1] 2 3 1 [[6]] [1] 2 1 3 ``` ```R > ?permn ``` ```R > permn(3, sum) [[1]] [1] 6 [[2]] [1] 6 [[3]] [1] 6 [[4]] [1] 6 [[5]] [1] 6 [[6]] [1] 6 ``` ```R > x <- LETTER[1:5] > length(permn(x)) [1] 120 ``` ```R > factorial(5) [1] 120 ``` ## Ejercicio 2 ```R > x <- LETTERS[1:5] > y <- sample(x, 10, replace=TRUE) > y [1] "B" "E" "A" "B" "B" "D" "D" "D" "B" [10] "A" ``` ```R > t <- table(y) > t y A B D E 2 4 3 1 barplot(t) ``` ```R > sum(t) [1] 10 ``` ```R > tf <- t / sum(t) > tf y A B D E 0.2 0.4 0.3 0.1 ``` ```R barplot(tf) ``` Para ver los porcentajes: ```R > tp <- t / sum(t) * 100 > tp y A B D E 20 40 30 10 ``` ## Ejercicio Repetir el ejercicio anterior pero con: > ¿Cuantos mensajes telegraficos se pueden mandar con 5 puntos y 3 rayas ?