2.2 basic grammar of R language

2.2 R Basic grammar of language

2.2.1 data structure —— Vector structure

A vector is a one-dimensional simple array , Can store numeric , Character and logical data .

First, we use the most primitive and clumsy method to create a vector

function ：c()

Using this function to create a vector is similar to SAS perhaps MATLAB Programming language , Both can be used. “=” To assign a value to a variable , Of course R It also has its own unique side , stay R In language , We can also use “<-” To assign a value to a variable , Give me a chestnut

For example, we want to give variable names a,b,c Assignment of three variables of , The assignment types are numerical , Character type and logical type , We can carry out the following operations ：

It should be noted that ：

1. Character type input requires quotation marks
2. Logical TRUE and FALSE Should be capitalized （ The point here is ： I use it Rstudio Write the program , So in the input TRUE and FALSE If you lose in lowercase , The system will pop you up automatically Capitalize option to , Just press enter , Therefore, it is highly recommended that you download and use Rstudio It's really convenient ！）

Finally, we can get the following results ：

Now let's learn some more advanced functions

function ：seq（）

This function is used to create vector groups with a specified step size or a specified number （ If you do not set the step size and number by yourself, it defaults to 1）, Examples are as follows ：

Specify the step size ：

 

Specified number ： 

 

We need to pay attention to ： You must have a starting value to make the function run

function ：rep（）

The main purpose of this function is to duplicate elements , Because of different replication methods , We can specify different replication methods on the suffix in brackets , Because there are too many replication methods , So here we will only talk about the most basic usage and take an example of copying the element at the specified location for a specified number of times , If you need to ask Du Niang directly for the rest of the methods in practical application ！

Examples of the most basic methods of use ： The digital 1 Copy 6 All over ：

 

An example of copying a specified location element for a specified number of times , Put the second element （2） And the fourth element （4） Copy 2 Time , Others are 1 Time ：

 

 

Finally, let's talk about the splicing of vectors ：

Functions that splice vectors by line ：rbind()

  Function of splicing vectors by column ：cbind()

About the operation of vectors, you can search directly on the Internet , Many bloggers have summarized many tables of algorithms, which are very complete, and you can easily find them , I will not introduce more here , What I want to emphasize here is , When we use “+” When splicing two vectors with different lengths , The system will automatically splice the short vectors into a vector with the same length as the long vector from beginning to end, and then calculate , And this process can only be carried out when the length of the long vector is an integral multiple of the length of the short vector , Otherwise, the system will automatically report an error , for example ：

All right. , That's it this time , Thank you for your support ！！