Extracting column from DataTable

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I have scenario like below:

  Scenario: do something interesting
    Given the following users
      | first_name | last_name | address |
      | John       | Doe       | add1    |
      | Jane       | Doe       | add2    |

How can I extract list of elements, as example: from first_name column.

I've tried to use cucumber.api.DataTable, but looks like it uses for other purposes.

I can extract only rows and then manage it as I want.

The most readable option in my opinion would be the asMaps method, that way you are independent of the ordering of columns:

@Given("^the following users$")
public void the_following_users(DataTable table) {
    for (Map<String, String> row : table.asMaps(String.class, String.class)) {
        System.out.println(row.get("first_name"));
    }
}

Extracting a single column of a DataTable is not part of its api, so you would have to implement that yourself in java.

How to retrieve one column from data table? - Academy, Hi All, I need to pull out the column names for a datatable, looking at various methods on the internet im not sure whats the best or most efficient  Command to Extract a Column as a Data Frame The following represents a command which can be used to extract a column as a data frame. If you use a command such as df[,1], the output will be a

i'm guessing you just want a List, but since you're using raw jdbc calls, you still have to traverse the ResultSet. you would need to craft your query to just return the one column and then extract each single item row into your result List object.

now if you were using JPA, you could fetch the result into a List by crafting your query to just return the one column and JPA would automatically unwrap it into a List (or List for other types like Date or Integer).

Best way of extracting column names from a datatable, Say column 5 is named "region" and you really must extract that column as a vector not a data.table. It is more robust to use the column name  5 Answers 5. Here you are just selecting the columns you want from the original data frame and creating a variable for those. If you want to modify the new dataframe at all you'll probably want to use .copy() to avoid a SettingWithCopyWarning.

Please try this code, it will give you the value under "first_name" column. If you have multiple rows, then use this code in loop

`@Given("^the following users$")
public void the_following_users(DataTable records) 
{
    for (Map<String, String> row : records.asMaps(String.class, String.class)) 
    { 
        System.out.println(row.get("first_name").intern());
    }
}`

Frequently Asked Questions about data.table, We therefore return a data.table with all columns from flights at rows for those row indices. – Sort flights first by column origin  There is an issue with this syntax because if we extract only one column R, returns a vector instead of a dataframe and this could be unwanted: > df[,c("A")] [1] 1. Using subset doesn't have this disadvantage. – David Dorchies Jul 27 '16 at 13:49 |

Introduction to data.table, You need [[]] as otherwise you are attempting to index the row. a[[col_names[1]]]. How do I extract a column from a data.table as a vector by its position? Below are some code snippets I have tried: DT<-data.table(x=c(1,2),y=c(3,4),z=c(5,6)) DT # x y z #1: 1 3 5 #2: 2 4 6

Extract datatable column by indexing a character vector, Such an object is automatically configured according to the schema defined for the DataTable through its collection of DataColumn objects. After creating a new​  Accessing pandas dataframe columns, rows, and cells At this point you know how to load CSV data in Python. In this lesson, you will learn how to access rows, columns, cells, and subsets of rows and columns from a pandas dataframe.

DataTable.Rows Property (System.Data), DataTables API instance with data for each cell in the selected columns in the result set. This is a 2D array with the top level array entries for each column matched  You can additionally use dataTable(0)(0).Note though that this way of accessing data gives you Object type variables, if you know the specific data type at the given position, you can access it by its actual type with for example dataTable(0).Field(Of String)(0) or row.Field(Of DateTime)(0) for String or DateTime contents.

Comments
  • do you need the rows or only the columns? if you only need the columns, then you should rotate your table. There is no direct way to only access columns