Data may be entered into R in a number of ways. Three commonly used methods will be discussed.
Perhaps the easiest way to enter small datasets is to enter each variable individually and then combine them into a data frame. Using the data from BPS7e problem 29.48, this might look like:
sex = c(rep("Female",12),rep("Male",7))
mass = c(36.1, 54.6, 48.5, 42.0, 50.6, 42.0, 40.3, 33.1, 42.4,
34.5, 51.1, 41.2, 51.9, 46.9, 62, 62.9, 47.4, 48.7, 51.9)
rate = c(995, 1425, 1396, 1418, 1502, 1256, 1189, 913, 1124, 1052,
1347, 1204, 1867, 1439, 1792, 1666, 1362, 1614, 1460)
gender = c(rep(1,12),rep(2,7))
bps7.29.48 = data.frame(sex, mass, rate, gender)We can now check to see if the data frame has been created by entering:
ls()## [1] "bps7.29.48" "gender" "mass" "rate" "sex"Note that the listing also shows the individual variables that were used to create the data frame. These can be deleted by using rm().
rm("sex", "mass", "rate", "gender")
ls()## [1] "bps7.29.48"The attributes of the data frame and some summary statistics can be computed using the attributes and summary functions.
attributes(bps7.29.48)## $names
## [1] "sex" "mass" "rate" "gender"
##
## $class
## [1] "data.frame"
##
## $row.names
## [1] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 summary(bps7.29.48)## sex mass rate gender
## Length:19 Min. :33.10 Min. : 913 Min. :1.000
## Class :character 1st Qu.:41.60 1st Qu.:1196 1st Qu.:1.000
## Mode :character Median :47.40 Median :1396 Median :1.000
## Mean :46.74 Mean :1370 Mean :1.368
## 3rd Qu.:51.50 3rd Qu.:1481 3rd Qu.:2.000
## Max. :62.90 Max. :1867 Max. :2.000Notice that while sex was treated as a categorical variable, gender was treated as if it was cardinal. R is smart in that it recognizes the difference between cardinal and categorical (which it calls ``factor’’) variables. To make gender a factor variable we can enter
bps7.29.48$gender = factor(bps7.29.48$gender,levels=c(1,2),labels=c("F","M"))Using summary we can see that gender is treated as a factor, or categorical, variable.
summary(bps7.29.48)## sex mass rate gender
## Length:19 Min. :33.10 Min. : 913 F:12
## Class :character 1st Qu.:41.60 1st Qu.:1196 M: 7
## Mode :character Median :47.40 Median :1396
## Mean :46.74 Mean :1370
## 3rd Qu.:51.50 3rd Qu.:1481
## Max. :62.90 Max. :1867RStudio will read comma and tab delimited text files. The data for BPS7e can be downloaded from http://bcs.whfreeman.com/bps7e. Save the PC-Text.ZIP file to your drive. Then, extract to files. Within the folder that is created will find a number of “Chapter” folders. Each of these has a number of files corresponding to examples (eg—–.txt files) and exercises (ex——.txt files).
We can use the GUI interface to import the file. Select Tools -> Import Dataset -> From Local File and navigate to the ex29-48METAB2.txt file. Double click on the file or enter its name in the File Name area and click Open.
In the new window, change the Name to something that is fairly easy to type. In this case we can use bps7.29.48 to represent the 48th exercise from the 29th chapter of BPS7e. Be sure that Heading is set to Yes. Note that the file is tab delimited and not comma separated. The rest of the default values are probably okay. Click on Import.
Rstudio will now submit view(bps7.29.48) to the console so that you can check to see if the file was properly imported.
R has a utility for reading comma separated value (CSV) ASCII files. These files can reside on the host machine or on a server. If the files are in standard CSV format, either of:
# To make the next line work you will have to change the path
HtWt = read.csv("htwt.csv")
summary(HtWt)## Height Weight Group
## Min. :51.0 Min. : 82.0 Min. :1.00
## 1st Qu.:56.0 1st Qu.:108.2 1st Qu.:1.00
## Median :59.5 Median :123.5 Median :2.00
## Mean :62.1 Mean :139.6 Mean :1.55
## 3rd Qu.:68.0 3rd Qu.:166.8 3rd Qu.:2.00
## Max. :79.0 Max. :228.0 Max. :2.00 # This reads the file from the given URL
htwt = read.csv("http://facweb1.redlands.edu/fac/jim_bentley/downloads/math111/htwt.csv")
summary(htwt)## Height Weight Group
## Min. :51.0 Min. : 82.0 Min. :1.00
## 1st Qu.:56.0 1st Qu.:108.2 1st Qu.:1.00
## Median :59.5 Median :123.5 Median :2.00
## Mean :62.1 Mean :139.6 Mean :1.55
## 3rd Qu.:68.0 3rd Qu.:166.8 3rd Qu.:2.00
## Max. :79.0 Max. :228.0 Max. :2.00will create a data frame that contains the htwt data. Note the use of forward slashes instead of backslashes.
The group variable will be imported as a numeric. To help R function efficiently, it will need to be converted to a factor variable using the method from above.
Regardless of how they were created, data frames may be saved in R as part of the R workspace. The workspace contains all of the variables, data frames, and functions that you have defined. A workspace is a snapshot of your work to the point of the save.
In RStudio, to save a workspace click on Session -> Save Workspace As. Navigate to the folder in which you wish to save the file and provide a descriptive file name. Now click on Save. Your workspace is now safely tucked away on your drive. This file can later be Loaded or you can open it by double clicking on the file.
History files store the commands that you used during your R session. These can be saved and loaded in a manner similar to that of workspaces. These files are are text files and can be edited using Wordpad or something similar. RStudio hides these behind a tab in the upper right window.