Df

A dataframe for Dart

Usage

Create

From csv:

final df = await DataFrame.fromCsv('dataset/stocks.csv');

fromCSV parses files according to the csv standard, including support for escape double quotes (see: RFC4180).

Note: the type of the records are infered from the data. The first line of the csv must contains the headers for the column names. Optional parameters:

dateFormat: the string format of the date: reference. Ex: MMM dd yyyy

timestampCol: the column to be treated as a timestamp. Ex: timestamp

timestampFormat: the format of the timestamp: seconds, milliseconds or microseconds. Ex: TimestampFormat.microseconds

verbose: set to true to print some info

From records:

final rows = <Map<String, dynamic>> rows[
   <String, dynamic>{'col1': 21, 'col2': 'foo', 'col3': DateTime.now()},
   <String, dynamic>{'col1': 22, 'col2': 'bar', 'col3': DateTime.now()},
];
final df = DataFrame.fromRows(rows);

Select

final List<Map<String, dynamic>> rows = df.rows;
// select a subset of rows
final List<Map<String, dynamic>> rows = df.subset(0,100);
/// select records for a column
final List<double> values = df.colRecords<double>('col2');
/// select list of records
final List<List<dynamic>> records = df.records;

Mutate

Add data:

// add a row
df.addRow(<String,dynamic>{'col1': 1, 'col2': 2.0});
// add a line of records
df.addRecord(<dynamic>[1, 2.0]);

Remove data:

df.removeFirstRow();
df.removeLastRow();
// remove the third row
df.removeRowAt(2);
// limit the dataframe to 100 rows starting from index 30
df.limit(100, startIndex: 30);

Copy a dataframe:

// get a new dataframe from the existing one
final DataFrame df2 = df.copy_();
// get a new dataframe with limited data
final DataFrame df2 = df.limit_(100);

Count

Nulls and zeros:

final int n = df.countNulls_('col1');
final int n = df.countZeros_('col1');

Columns:

final int mean = df.mean('col1');
final int sum = df.sum('col1');
final int max = df.max('col1');
final int min = df.min('col1');

Info

final int numRecords= df.length;
final List<DataFrameColumn> cols = df.columns;
final List<String> colNames = df.columnsNames;
// print info and sample data
df.head();
// like head with a bit more details
df.show();

Conventions

All the dataframe operations are inplace. All the methods that return objects end with an underscore. Example:

// inplace
df.limit(30);
// get a new dataframe with limited data
final DataFrame df2 = df.limit_(30);

Vocabulary conventions:

• A row is a map of key/values pair
• A record is a single cell value
• An index is a row position
• An indice is a column position