2020. 2. 14. 16:46ㆍ카테고리 없음
. read.csv: for reading “comma separated value” files (“.csv”). read.csv2: variant used in countries that use a comma “,” as decimal point and a semicolon “;” as field separators.
read.delim: for reading “tab-separated value” files (“.txt”). By default, point (“.”) is used as decimal points. read.delim2: for reading “tab-separated value” files (“.txt”). By default, comma (“,”) is used as decimal points.The simplified format of these functions are, as follow: # Read tabular data into Rread.table(file, header = FALSE, sep = ', dec = '.' )# Read 'comma separated value' files ('.csv')read.csv(file, header = TRUE, sep = ',', dec = '.'
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.)# Or use read.csv2: variant used in countries that# use a comma as decimal point and a semicolon as field separator.read.csv2(file, header = TRUE, sep = ';', dec = ','.)# Read TAB delimited filesread.delim(file, header = TRUE, sep = 't', dec = '.' .)read.delim2(file, header = TRUE, sep = 't', dec = ','.). Reading a local file. To import a local.txt or a.csv file, the syntax would be:# Read a txt file, named 'mtcars.txt'mydata.
When a program runs, the data is in the memory but when it ends or the computer shuts down, it gets lost. To keep data permanently, we need to write it to a file.File is used to store data. In this topic, we will learn about reading data from a file and writing data in the file.First of all, let's see how to declare a file.File is declared using a pointer of type file as follows.FILE.fr;We can perform many functions with files. Some of these functions are listed below.FunctionDescriptionfopencreate a new file or open a existing filefcloseclose a filefgetcread a character from a filefputcwrite a character to a filefscanfread a string from a filefprintfwrite a string to a fileLet’s see how to write data in a file, open, close or read a file.Opening a fileWe open a file or create a new file using fopen function.
Let's look at the syntax of fopen. This is test These are content in prog.txt in my system.In the above example, firstly we opened a file named 'prog.txt' in read mode so that we can read data from the file. For this, 'prog.txt' must exist in your computer.In while loop, fgetc(fr) reads the value of c from the file 'prog.txt'. When the entire value of 'c' has been read from the file and EOF (End of file) is reached, fclose(fr) closes the file.As simple as that!We read the contents of the file with fgetc using variable 'c'. In while, printf function prints the value of c on the screen. After this, we will close the file using fclose.Using fscanf and fprintfWhile getc and putc are used for characters, we use fscanf and fprintf to read and write string to a file.Let's understand with the help of an example.
Enter a string and a number Test 49 Test 49Here, we first created a file named 'welcome.txt' and opened it in write mode using fopen function. Then, we input a string and an integer value from the keyboard using scanf function and stored the values in variables 's' and 't' respectively.Then, fprintf writes both the string and integer values to the file. After that, fclose(fr) closes the file.Now, we will read the contents of the file and then print those on the screen.
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For that, we will first open the file in read mode using fopen function. After that, fscanf function will read the contents of the file and printf function will display the contents of the file on the screen.Now see this program to copy one file to another.