R-Function Memo

1. View Object type:

Class ()

Mode ()

STR ()

2. The difference between parameter test and non-parameter test:

3, the query matrix and data frame a row, a column of the difference:

Matrix: With square brackets [], subscript or column name, comma "," The three selected;

Data frame: with square brackets [], the Subscript or column name is selected. The package uses $. In general, only the columns of the data frame are selected, the rows are not selected, and the subscript + comma [1,] is used, unless you want to select a row.

Common denominator: When you select multiple rows or columns, use the C () function.

In order to filter a variable according to certain conditions, regardless of the matrix and data frame, add a comma "," for the vector without commas.

Such as

　　Matrix Examples:

Select a column:

　　Data Frame Example :

4, two and above statements in a line, you must use a semicolon, separated, written in multiple lines, you can not write a semicolon;

Such as:

Or

R-Function Memo