R Vectors

R statistical package ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

R prompt R version 2.6.1 (2007-11-26) Copyright (C) 2007 The R Foundation for Statistical Computing ISBN 3-900051-07-0 R is free software and comes with ABSOLUTELY NO WARRANTY. You are welcome to redistribute it under certain conditions. Type 'license()' or 'licence()' for distribution details. Natural language support but running in an English locale R is a collaborative project with many contributors. Type 'contributors()' for more information and 'citation()' on how to cite R or R packages in publications. Type 'demo()' for some demos , 'help()' for on-line help, or 'help.start()' for an HTML browser interface to help. Type 'q()' to quit R. >

Usare R ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

R HTML Help System > help.start()

R: Valutazione di Espressioni ,[object Object],[object Object],[object Object],[object Object],In R tutte le espressioni restituiscono un valore ma il valore puo’ essere NULL o invisibile. Alcune espressioni sono importanti non per il loro risultato, ma per gli “effetti secondari” che generano, per esempio il comando: > help(mean) Non stampa niente a video, ma ha l’interessante effetto secondario di aprire la pagina help di R relativa al comando mean

Linguaggio Object-Oriented ,[object Object],[object Object],[object Object],[object Object],[object Object],In R ogni cosa e’ un oggetto ed ogni oggetto appartiene ad una classe MyArray = new Array MyArray Class Array data function: pop function: push In R: S3 and S4 classes

Creazione di Oggetti in R ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Nomi di Variabili in R ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Workspace ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Working Directory ,[object Object],[object Object],[object Object],[object Object],> setwd("/Users/default/Desktop/R_DRAFT") > getwd() [1] "/Users/default/Desktop/R_DRAFT" > dir() [1] "LASTPRDM.txt" "PRDM_27_3_2007.log"

Tipologie di Dati ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Vettori ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Vettori: c() and length() ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Accedere agli elementi di un Vettore ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Inizializzazione e Riempimento ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Metodi per costruire un vettore in R ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Metodi per costruire un vettore: scan() ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],copy paste <ENTER> <ENTER>

I vettori possono contenere un solo tipo di dati ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Indice di un Vettore ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],9 8 7 6 5 4 3 2 1 0 -1 -2 -3 -4 [14] [13] [12] [11] [10] [9] [8] [7] [6] [5] [4] [3] [2] [1]

Cercare elementi in un Vettore ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],9 8 7 6 5 4 3 2 1 0 -1 -2 -3 -4 [14] [13] [12] [11] [10] [9] [8] [7] [6] [5] [4] [3] [2] [1]

Operatori di comparazione e operatori logici Diverso da … Maggiore o uguale a … Minore o uguale a … Uguale a … Maggiore di … Minore di … Significato x != 2 != x >= 2 >= x <= 2 <= x == 2 == x > 2 > x < 2 < Esempio Operatore NOT OR AND Significato x > 2 ! x == 4 ! x > 2 | x == 0 | x < 2 & x != 0 & Esempio Operatore

Accedere agli elementi di un Vettore: altri comandi ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],9 8 7 6 5 4 3 2 1 0 -1 -2 -3 -4 [14] [13] [12] [11] [10] [9] [8] [7] [6] [5] [4] [3] [2] [1]

Valori mancanti (NA) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],> x <- c(NA,1,2,3,NA,NA) > x [1] NA 1 2 3 NA NA > is.na(x) [1] TRUE FALSE FALSE FALSE TRUE TRUE > which(is.na(x)) [1] 1 5 6 > x[!is.na(x)] [1] 1 2 3 > x <- c(NA,1,2,3,NA,NA) > mean(x) [1] NA > mean(x, na.rm=TRUE) [1] 2

La funzione mean: na.rm > help(mean)

Operazioni algebriche ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],> help(Arithmetic)

Altre operazioni algebriche Coseno cos() Seno sin() Logaritmo in base 10 log10 Logaritmo in base 2 log2() Logaritmo log() Exponential function (e) exp() Valore assoluto abs() Radice quadrata sqrt()

Altre utili operazioni con i vettori ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],> y <- c(2,7,4,1) > y [1] 2 7 4 1 > rev(y) [1] 1 4 7 2 > sort(y) [1] 1 2 4 7 > rev(sort(y)) [1] 7 4 2 1 > sum(y) [1] 14 > sum(y[y>2]) [1] 11 > sum(y>2) [1] 2

Factors ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

NOTA: Espressioni e oggetti ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Espressioni e oggetti: polimorfismo ,[object Object],[object Object],[object Object],> x <- rnorm(100, mean=10,sd=2) > class(x) [1] "numeric" > summary(x) Min. 1st Qu. Median Mean 3rd Qu. Max. 5.189 8.401 9.603 9.625 10.890 14.850 > x <- factor(vettore, levels=classi, ordered=T) > summary(x) giovane anziano adulto 10 5 7

Utili operazioni di ricodifica ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

R Vectors

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