mainframe is a C++ dataframe library. It features C++ container ergonomics like iterators, copy-on-write column data management, and a flexible expression syntax that allows for efficient row filtering and column population.
mainframe supports flexible data of nearly any type for columns including user-defined types.
frame<year_month_day, mi<double>, bool> f1;
f1.set_column_names( "date", "temperature" , "rain" );
f1.push_back( 2022_y/January/1, 8.9, false );
f1.push_back( 2022_y/January/2, 10.0, false );
f1.push_back( 2022_y/January/3, missing, true );
f1.push_back( 2022_y/January/4, 12.2, false );
f1.push_back( 2022_y/January/5, 13.3, false );
f1.push_back( 2022_y/January/6, 14.4, true );
f1.push_back( 2022_y/January/7, missing, false );
f1.push_back( 2022_y/January/8, 9.1, true );
f1.push_back( 2022_y/January/9, 9.3, false );
std::cout << f1;
| date | temperature | rain
__|____________|_____________|_______
0| 2022-01-01 | 8.9 | false
1| 2022-01-02 | 10 | false
2| 2022-01-03 | missing | true
3| 2022-01-04 | 12.2 | false
4| 2022-01-05 | 13.3 | false
5| 2022-01-06 | 14.4 | true
6| 2022-01-07 | missing | false
7| 2022-01-08 | 9.1 | true
8| 2022-01-09 | 9.3 | false
mainframe supports an expression format that allows for simple row filtering. Here, fcoldandrain is a new dataframe that will contain a single row for 2022/January/8:
auto fcoldandrain = f1.rows( _1 <= 12 && _2 == true && _0 > 2022_y/January/4 );
// could also have used
// auto fcoldandrain = f1.rows(
// []( auto&/*b*/, auto& c, auto&/*e*/ ) {
// return c->at( _1 ) <= 12 && c->at( _2 ) == true && c->at( _0 ) > 2022_y/January/4; } );
// b, c, and e are frame iterators
std::cout << fcoldandrain;
| date | temperature | rain
_|____________|_____________|_______
0| 2022-01-08 | 9.1 | true
Expressions also work well for creating new data columns
auto f2 = f1.new_series<year_month_day>( "next year", _0 + years(1) );
std::cout << f2;
| date | temperature | rain | next year
__|____________|_____________|_______|____________
0| 2022-01-01 | 8.9 | false | 2023-01-01
1| 2022-01-02 | 10 | false | 2023-01-02
2| 2022-01-03 | 11.1 | true | 2023-01-03
3| 2022-01-04 | 12.2 | false | 2023-01-04
4| 2022-01-05 | 13.3 | false | 2023-01-05
5| 2022-01-06 | 14.4 | true | 2023-01-06
6| 2022-01-07 | 15.5 | false | 2023-01-07
7| 2022-01-08 | 9.1 | true | 2023-01-08
8| 2022-01-09 | 9.3 | false | 2023-01-09
// column references like _0, _1, and _2 can have indexers to previous or
// following rows like _0[3] or _1[-1]
auto f3 = f2.new_series<mi<bool>>( "temp predicted rain", _1[-1] <= 10.0 && _2 == true ) );
std::cout << f3;
| date | temperature | rain | next year | temp predicted rain
__|____________|_____________|_______|____________|_____________________
0| 2022-01-01 | 8.9 | false | 2023-01-01 | missing
1| 2022-01-02 | 10 | false | 2023-01-02 | false
2| 2022-01-03 | 11.1 | true | 2023-01-03 | true
3| 2022-01-04 | 12.2 | false | 2023-01-04 | false
4| 2022-01-05 | 13.3 | false | 2023-01-05 | false
5| 2022-01-06 | 14.4 | true | 2023-01-06 | false
6| 2022-01-07 | 15.5 | false | 2023-01-07 | false
7| 2022-01-08 | 9.1 | true | 2023-01-08 | false
8| 2022-01-09 | 9.3 | false | 2023-01-09 | false