Introduction to R and R-Studio Getting Data Into R. 1. Enter Data Directly into R...

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1 Introduction to R and R-Studio Getting Data Into R 1. Enter Data Directly into R Import Excel Data (.xlsx ) into R Import Stata Data (.dta ) into R a) From a folder on your computer.... b) From the internet. 4. Import SAS Data (.sas7bdat ) into R.. 5. Describe Your Data Set Structure List Your Data Please note I do a lot of comments! You will see many of my commands that begin with the pound sign (#). They re also in green. While recommended, you don t actually have to type these comments. R handout 02 Fall 2017 Getting Data into R.docx Page 1 of 8

2 1. Enter Data Directly into R R is all about objects. Data in R is, thus, an object Each command is an assignment to an object. objectname <- Type here the stuff that you are assigning to objectname Direct Entry of Data for a Single Variable using the command c(value, value, value, etc) # Enter data on weight for n=4 into column vector called weight <- c(value,value,value,value) weight <- c(161.3,120.1,223.2,124.0) weight [1] Direct Entry of Data for Multiple Variables using c(value, value, etc) and data.frame (column,column, etc) # Enter data on weight for n=4 into column vector called weight # Repeat for age # Repeat for study id weight <- c(161.3,120.1,223.2,124.0) age <- c(54,36,78,62) studyid <- c(1,2,3,4) # Bind columns of data into a single matrix <- data.frame(column,column,colum) labdata1 <- data.frame(studyid,age,weight) labdata1 studyid age weight R handout 02 Fall 2017 Getting Data into R.docx Page 2 of 8

3 2. Import Excel Data (.xlsx ) into R Importing Excel Data into R Requires 2 or 3 Steps First. (This is a one time step) Install the package openxlsx Second. Attach (load) the package to your R Environment Third. Import Excel data 1. How to Install the Package openxlsx install.packages( openxlsx ) Example - Here is a screen capture of my installation of openxlsx R handout 02 Fall 2017 Getting Data into R.docx Page 3 of 8

4 2. Attach (Load) the package openxlsx to your R Environment library(openxlsx) 3. Import Excel Data using function read.xlsx( ) # Import Excel data (R_lab1.xlsx) into R object (excel_import) <- read.xlsx( full path/r_lab1.xlsx ) excel_import <- read.xlsx( /Users/cbigelow/Desktop/R_lab1.xlsx ) excel_import id dob gender weight male female male female Alternatively, under the Packages tab, select Install and type openxlsx in the dialogue box. Click Install to complete this step. R handout 02 Fall 2017 Getting Data into R.docx Page 4 of 8

5 3. Import Stata Data (.dta ) into R No surprises here. The steps are similar to those for importing Excel data into R. Importing Stata Data into R Requires 2 or 3 Steps First. (Again, this is a one time step) Install the package foreign Second. Attach (load) the package to your R Environment Third. Import Stata data 1. How to Install the Package foreign install.packages( foreign ) OR install the package using the Packages tab. 2. Attach (Load) the package foreign to your R Environment library(foreign) 3a. Import Stata Data From a Folder on Your Computer using function read.dta( ) # Import Stata data (larvae.dta) into R object (larvae_data) <- read.dta( full path/larvae.dta ) larvae_data <- read.dta( /Users/cbigelow/Desktop/larvae.dta ) larvae_data id y x1 x some rows skipped b. Import Stata Data From the Internet using function read.dta( ) # Import Stata data (week02.dta) into R object (week02_data) # url <- full url url <- week02_data <- read.dta(file=url) R handout 02 Fall 2017 Getting Data into R.docx Page 5 of 8

6 4. Import SAS Data (.sas7bdat ) into R Importing SAS Data into R Requires 3 Steps First. (Again, this is a one time step) Install the package haven Second. Attach (load) the package to your R Environment Third. Import SAS data 1. How to Install the Package haven install.packages( haven ) OR install the package using the Packages tab. 2. Attach (Load) the package haven to your R Environment library(haven) 3. Import SAS Data using function read_sas( ) # Import SAS data (example.sas7bdat) into R object (example) <- read_sas( full path/larvae.dta ) example <- read_sas( /Users/cbigelow/Desktop/sasexample.sas7bdat ) example id dob gender weight male female male female R handout 02 Fall 2017 Getting Data into R.docx Page 6 of 8

7 5. Describe Your Data Set Structure # Observations, # Variables Display variable names R Command colnames(larvae_data) Display number of rows (observations) nrow( ) nrow(larvae_data) [1] 15 Display number of columns (variables) ncol( ) Display dimensions of data set frame (rows x columns) (# observations x # variables) ncol(larvae_data) [1] 4 dim( ) dim(larvae_data) [1] 15 4 Detailed Structure of Data command str(dataframe) # str(dataframe) str(larvae_data) 'data.frame': 15 obs. of 4 variables: $ id: num $ y : num $ x1: num $ x2: num attr(*, "datalabel")= chr "PubHlth 640 Unit 2 Regression - Larvae data" - attr(*, "time.stamp")= chr "10 Feb :36" - attr(*, "formats")= chr "%9.0g" "%9.0g" "%9.0g" "%9.0g" - attr(*, "types")= int attr(*, "val.labels")= chr "" "" "" "" - attr(*, "var.labels")= chr "larva id" "log10(survival)" "log10(dose)" "log10(weight)" - attr(*, "expansion.fields")=list of 2..$ : chr "_dta" "note1" "\"Week 3 homework assignment exercises 2 and 3\""..$ : chr "_dta" "note0" "1" - attr(*, "version")= int 12 R handout 02 Fall 2017 Getting Data into R.docx Page 7 of 8

8 6. List Your Data Use Subscripts to Select a Subset of Your Data Just like spreadsheets in Excel or Stata data sets, rows are observations and variables are columns To select a subset of your data requires using subscripts, which can be thought of as addresses. Subscripts appear in square brackets and are of the form: dataframe[1 st subscript is for rows, 2 nd subscript is for columns] = [observation selection, variable selection] List First 6 observations using head( ) List Last 6 observations using tail( ) List Entire Data Set (be careful!): Two ways: 1) Just type its name; or 2) View(dataframe). List Selected Observations: For observations 8, 9, 10, list the data for all variables List Selected Variables: For all observations, List the observations for only the 2 nd variable List Selected Variables on Selected Observations: For observations 8, 9, 10 only, List the observations for only the 2 nd variable R Command head(larvae_data) tail(larvae_data) larvae_data View(larvae_data) larvae_data[8:10,] id y x1 x larvae_data[,2] [1] larvae_data[8:10,2] [1] R handout 02 Fall 2017 Getting Data into R.docx Page 8 of 8