Files,blocks and functions in R
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This document discusses various concepts in R including reading and writing data files, lists, data frames, conditional statements, loops, and functions. It explains how to read data from files using read.table() and write data to files using write.table(). Lists can be used to store heterogeneous data in a single object. Data frames allow storing data in a tabular form with rows and columns. Conditional statements like if/else and loops like for and while allow repeating blocks of code. Functions are objects that return a value for given arguments.
![Lists
For saving of heterogeneous data in the one object lists can be
used. For example:
> x1 = c("Milk", "Yogurt", "Sour cream", "Curd")
> x2 = c(1, 1, 14, 7)
> x3 = c(TRUE, FALSE)
> l1 = list(Text = x1, Number = x2, Logic = x3)
> l1
To identify specific elements of the list such constructions can be
used :
l1$Text[3]; l1$Text;
l1[[1]][2]; l1[[2]].](https://image.slidesharecdn.com/filesblocksfunctionsinr2-140527225940-phpapp01/85/Files-blocks-and-functions-in-R-6-320.jpg)
![Comments, blocks of expressions
Any comment begins with the character #. The test located in
the line after this character not regarded as part of the program
to be executed.
Expressions can be combined into blocks with curly braces.
The result of the expressions block is the result of the last of
them.
> {
+ x = 9;
+ y = 4;
+ x + y;
+ }
[1] 13](https://image.slidesharecdn.com/filesblocksfunctionsinr2-140527225940-phpapp01/85/Files-blocks-and-functions-in-R-10-320.jpg)
Files,blocks and functions in R
- 1. DATA FILES, BLOCKS OF EXPRESSIONS, CYCLES AND FUNCTIONS IN R Vladimir Bakhrushin, Professor, D.Sc. (Phys. & Math.) [email protected]
- 2. Data reading > data<-read.table(“File name", sep=";", dec=",", header=TRUE, …) first argument is a reference to the file of *.csv format, that contains data; argument sep indicates, by which sign the data are separated; argument dec indicates decimal separator for numbers; argument header indicates whether the first cells of each column are the column names; argument row.names indicates whether one of columns contains the row names; argument nrows specifies the number of lines that need to be read from the table.
- 3. Data reading
- 4. Writing data to a file write.table(x, file = "", append = FALSE, quote = TRUE, sep = " ", na = "NA", dec = ".", row.names = TRUE, col.names = TRUE, qmethod = c("escape", "double"), …) x – object that must be written to the file (usually it is a matrix or data table); file – name of the file to which the data must be written or other connections opened to writing; append – argument that indicates the need to append data to an existing file or to create a new file with the same name; quote – indicates the need to take in quotes marks of rows and columns; na – character set used for the missing values.
- 5. Writing data to a file write.table(a2, file = "a2.csv", sep = " ", dec = ".")
- 6. Lists For saving of heterogeneous data in the one object lists can be used. For example: > x1 = c("Milk", "Yogurt", "Sour cream", "Curd") > x2 = c(1, 1, 14, 7) > x3 = c(TRUE, FALSE) > l1 = list(Text = x1, Number = x2, Logic = x3) > l1 To identify specific elements of the list such constructions can be used : l1$Text[3]; l1$Text; l1[[1]][2]; l1[[2]].
- 7. Lists
- 8. Data frames
- 9. Data editing using function fix()
- 10. Comments, blocks of expressions Any comment begins with the character #. The test located in the line after this character not regarded as part of the program to be executed. Expressions can be combined into blocks with curly braces. The result of the expressions block is the result of the last of them. > { + x = 9; + y = 4; + x + y; + } [1] 13
- 11. Conditional constructs “If” – “else” statement is an example of conditional construct: if (<condition>) {<expression_1> }else{ <expression_2>}
- 12. Loops Loops with predetermined number of iterations can be organized using function “for”: for (<variable> in <expression_1>) <expression_2> If it is need to repeat iterations until a certain condition is fulfilled, we can use a loop “while”: while (<condition>) { <expression> }
- 13. Loops
- 14. Loops Infinite loops “Repeat” are used when a procedure should be executed if the interruption condition is not performed. Command “break” is used to interrupt the cycle, and command “next” – to interrupt the current iteration and move to the next one.
- 15. Functions Function in R is an object, that for a given set of arguments returns a certain value. Usually when the function is declared its value is assigned to some variable. <variabe> = function(<arguments>) { <expression> }. Subsequently, the function can be called using the construction: <result> = <variable>(<arguments>).
- 16. Functions
- 17. Functions
- 18. Literature 1. An Introduction to R 2. Introduction to the R Language: Functions 3. R Tutorial: An R introduction to statistics 4. Kelly Black. R Tutorial