Read All Data in a Folder R
Reading and Writing Data to and from R
Reading files into R
Ordinarily we will exist using data already in a file that we need to read into R in order to work on it. R can read data from a multifariousness of file formats—for case, files created as text, or in Excel, SPSS or Stata. We volition mainly be reading files in text format .txt or .csv (comma-separated, usually created in Excel).
To read an entire data frame straight, the external file will normally have a special grade
- The starting time line of the file should have a name for each variable in the data frame.
- Each additional line of the file has as its get-go item a row characterization and the values for each variable.
Here nosotros use the example dataset called airquality.csv and airquality.txt
Input file grade with names and row labels:
Ozone Solar.R * Wind Temp Month Day
1 41 ***** 190 ** 7.iv ** 67 **** 5 ** ane
2 36 ***** 118 ** 8.0 ** 72 **** 5 ** 2
3 12 ***** 149 * 12.6 ** 74 **** 5 ** three
iv 18 ***** 313 * 11.v ** 62 **** 5 ** 4
5 NA ***** NA ** 14.3 ** 56 **** 5 ** v
...
By default numeric items (except row labels) are read as numeric variables. This can be inverse if necessary.
The function read.tabular array() can then be used to read the data frame straight
> airqual <- read.table("C:/Desktop/airquality.txt")
Similarly, to read .csv files the read.csv() function can be used to read in the data frame directly
[Note: I have noticed that occasionally yous'll need to exercise a double slash in your path //. This seems to depend on the automobile.]
> airqual <- read.csv("C:/Desktop/airquality.csv")
In addition, y'all can read in files using the file.choose() office in R. Later on typing in this command in R, you lot tin can manually select the directory and file where your dataset is located.
- Read the airquality.csv file into R using the read.csv command.
- Read the airquality.txt file into R using the file.choose() control
Occasionally, you will need to read in data that does not already accept column name information. For example, the dataset BOD.txt looks like this:
i 8.3
ii 10.3
iii 19.0
iv 16.0
5 15.6
7 19.8
Initially, there are no column names associated with the dataset. We can use the colnames() command to assign column names to the dataset. Suppose that we want to assign columns, "Time" and "demand" to the BOD.txt dataset. To practice so we practice the following
> bod <- read.table("BOD.txt", header=F)
> colnames(bod) <- c("Time","need")
> colnames(bod)
[one] "Time" "demand"
The first command reads in the dataset, the control "header=F" specifies that at that place are no column names associated with the dataset.
Read in the cars.txt dataset and call it car1. Make sure you lot use the "header=F" choice to specify that there are no column names associated with the dataset. Next, assign "speed" and "dist" to be the offset and second column names to the car1 dataset.
The two videos below provide a nice explanations of different methods to read data from a spreadsheet into an R dataset.
Import Data, Copy Data from Excel to R, Both .csv and .txt Formats (R Tutorial 1.3) MarinStatsLectures [Contents
]
Importing Information and Working With Data in R (R Tutorial one.iv) MarinStatsLectures [Contents]
Writing Information to a File
Afterwards working with a dataset, we might like to relieve it for future use. Before we practice this, let's offset ready upwardly a working directory and so we know where we can find all our information sets and files afterward.
Setting upwardly a Directory
In the R window, click on "File" then on "Modify dir". You should then encounter a box popular up titled "Choose directory". For this class, choose the directory "Desktop" by clicking on "Browse", and so select "Desktop" and click "OK". In the future, you may want to create a directory on your figurer where yous go on your data sets and codes for this grade.
Alternatively, you lot can employ the setwd() role to assign equally working directory.
> setwd("C:/Desktop")
To notice out what your current working directory is, type
> getwd()
Setting Up Working Directories in R (R Tutorial one.viii) MarinStatsLectures [Contents]
In R, we can write data frames easily to a file, using the write.table() control.
> write.tabular array(cars1, file=" cars1.txt ", quote=F)
The start argument refers to the data frame to be written to the output file, the 2d is the proper noun of the output file. By default R will surround each entry in the output file by quotes, so nosotros use quote=F.
Now, let's bank check whether R created the file on the Desktop, by going to the Desktop and clicking to open the file. You should meet a file with three columns, the beginning giving the alphabetize (or row number) and the other two the speed and distance. R past default creates a cavalcade of row indices. If we wanted to create a file without the row indices, nosotros would use the control:
> write.table(cars1, file=" cars1.txt ", quote=F, row.names=F)
Datasets in R
Watch the video below for a concise intoduction to working with the variables in an R dataset
Working with Variables and Data in R (R Tutorial 1.five) MarinStatsLecures [Contents]
Around 100 datasets are supplied with R (in the package datasets), and others are available.
To see the list of datasets currently bachelor use the command:
data()
Nosotros will first look at a data set on CO2 (carbon dioxide) uptake in grass plants available in R.
> CO2
[ Note: capitalization matters here; also: it'southward the letter of the alphabet O, non nil. Typing this command should display the entire dataset called CO2, which has 84 observations (in rows) and v variables (columns).]
To go more information on the variables in the dataset, type in
> assistance(CO2)
Evaluate and report the mean and standard deviation of the variables "Concentration" and "Uptake".
Subsetting Data in R With Square Brackets and Logic Statements (R Tutorial i.6) MarinStatsLecures [Contents]
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Source: https://sphweb.bumc.bu.edu/otlt/MPH-Modules/BS/R/R1_GettingStarted/R1_GettingStarted8.html
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