introduction into r for historians (part 1: introduction)

Quantitave research methodsStatistical Software

Introducing R vocabularyGetting help

Installing R and RStudio

Introduction into R

Richard L. Zijdeman

28 May 2015

Richard L. Zijdeman Introduction into R




1 Quantitave research methods

2 Statistical Software

3 Introducing R vocabulary

4 Getting help

5 Installing R and RStudio





Quantitave research methods





Why

To answer descriptive and explanatory questions on populations





Workflow: PTE

problem (research question)theory (hypothesis)empirical test . . . with loops between T-E and P-T-E





Research Questions

descriptive (to what extent. . . )comparative (comparing two entities)

trend (comparison over time)

explanatory (focus on mechanism at hand)





Theory

deductive reasoningexplanans

general mechanismcondition

explanandum (hypothesis)





Empirical test

sample vs. populationrandom vs. stratified samplestesting technique, e.g.:

T-test, correlation, regression

Software required for faster analysis





Statistical Software





The dangers of analysing with spreadsheets(e.g. MS Excel)

tempting to input and clean data in the same sheetdifficult to track cleaning rulesdefaults mess up your data (e.g. 01200 -> 1200)





Why use syntax (scripting)

Efficiency (really)Quality (error checking)ReplicatabilityCommunication





R

R is open source, which is good and bad:

anybody can contribute (check, improve, create code)free of chargebut: R depends on collective action

cannot ‘demand’ supportsprawl of packages





RStudio

browser for Rprovides easy access to:

scriptsdataplotsmanual


http://www.rstudio.com




Introducing R vocabulary





R script

* series of commands to manipulate data* always save your script, NEVER change your data

original data + script = reproducable research





R Session

* contains scripts, data, functions* can be saved 'workspace image'* prefer not to:

+ sessions are usually cluttered+ only useful if running script takes time





Assignment

* 'attach' values to an object (e.g. a variable)

x <- 5y <- 4z <- x*yprint(z)

## [1] 20





Assignment II

Try and imagine the potential of assignment

x <- c(4, 3, 2, 1, 0, 27, 34, 35)# 'c' for concatenate valuesy <- -1z <- x*yprint(z)

## [1] -4 -3 -2 -1 0 -27 -34 -35





Data.frame

basically a tablecontains columns (variables)contains rows (cases)“flat table” in Kees’ terminology

my.df <- data.frame(x,z)str(my.df) # show STRucture

## 'data.frame': 8 obs. of 2 variables:## $ x: num 4 3 2 1 0 27 34 35## $ z: num -4 -3 -2 -1 0 -27 -34 -35





Packages and libraries

base R (core product)additional packages

CRAN repositoryspread through ‘mirrors’choose a local, but active mirror

Githubpackages not on CRANdevelopment versions of CRAN libraries


http://cran.r-project.org/mirrors.html

https://github.com/rstudio/ggvis




Getting help





Build-in help: “?”

?[function] / ?[package]e.g. “?plot” or “?graphics”

check the index for user guides and vignettes





Cran website

ManualsR FAQR Journal


http://cran.r-project.org

http://cran.r-project.org/manuals.html

http://CRAN.R-project.org/doc/FAQ/R-FAQ.html

http://journal.r-project.org/




Online communities

StackoverflowInstance of StackexchangeReputation based Q&A

Specific lists for packages, e.g.:ggplot2R-sig-mixed-models


http://stackoverflow.com

https://groups.google.com/forum/?fromgroups#!forum/ggplot2

https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models




Asking a question Getting an answer

Search the web: others must have had this problem tooIf you raise a question:

be politebe conciseshort backgroundreplicatable exampledebrief your efforts sofar





Download R

Instructions via http://www.r-project.orgChoose a CRAN mirrorhttp://cran.r-project.org/mirrors.html

close, but active too!Romania hasn’t gone (yet!)

Click on ‘Download R for Windows’Follow usual installation procedureDouble click on R

You should now have a working session!Close the session, do not save workspace image


http://www.r-project.org

http://www.r-project.org






RStudio

RStudio is found on http://www.rstudio.comDownload the version for your OS (e.g. windows)

http://www.rstudio.com/products/rstudio/download/

Install by double clicking on the downloaded fileStart RStudio by double clicking on the iconYou do not need to start R, before starting RStudio






introduction into r for historians (part 1: introduction)

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