Comments

Author: tedmiddleton

mainframe/frame.hpp

@@ -213,6 +213,32 @@ class frame
     frame<Ts..., T>
     append_column(const std::string& column_name) const;
 
+    /// Add a new column to the end of the frame with type T and initialize it
+    /// with a callable object like an expression
+    ///
+    ///     frame<year_month, int> f1;
+    ///     f1.set_column_names({"month", "length"});
+    ///     f1.push_back(2022_y/1, 1);
+    ///     f1.push_back(2022_y/2, 2);
+    ///     f1.push_back(2022_y/3, 3);
+    ///     frame<year_month, int, double> f2 = f1.append_column<double>("depth", _1 + 10.0);
+    ///     // f2 is now 
+    ///     //   |   month | length | depth
+    ///     // __|_________|________|_______
+    ///     //  0| 2022-01 |      1 |  11.0
+    ///     //  1| 2022-02 |      2 |  12.0
+    ///     //  2| 2022-03 |      3 |  13.0
+    ///     frame<year_month, int, double> f3 = 
+    ///         f2.append_column<double>("height", [](auto& beginit, auto& currit, auto& endit) {
+    ///             return currit->at(_1) + 20.0;
+    ///         });
+    ///     // f3 is now 
+    ///     //   |   month | length | depth | height
+    ///     // __|_________|________|_______|________
+    ///     //  0| 2022-01 |      1 |  11.0 |   21.0
+    ///     //  1| 2022-02 |      2 |  12.0 |   22.0
+    ///     //  2| 2022-03 |      3 |  13.0 |   23.0
+    ///
     template<typename T, typename Ex>
     frame<Ts..., T>
     append_column(const std::string& column_name, Ex expr) const;
@@ -474,6 +500,31 @@ class frame
     frame<T, Ts...>
     prepend_column(const std::string& column_name) const;
 
+    /// Add a new column to the beginning of the frame with type Tand initialize it
+    /// with a callable object like an expression
+    ///
+    ///     frame<year_month, int> f1;
+    ///     f1.set_column_names({"month", "length"});
+    ///     f1.push_back(2022_y/1, 1);
+    ///     f1.push_back(2022_y/2, 2);
+    ///     f1.push_back(2022_y/3, 3);
+    ///     frame<double, year_month, int> f2 = f1.prepend_column<double>("depth", _1 + 10.0);
+    ///     // f2 is now 
+    ///     //   | depth |   month | length 
+    ///     // __|_______|_________|________
+    ///     //  0|  11.0 | 2022-01 |      1 
+    ///     //  1|  12.0 | 2022-02 |      2 
+    ///     //  2|  13.0 | 2022-03 |      3 
+    ///     frame<year_month, int, double> f3 = 
+    ///         f2.prepend_column<double>("height", [](auto& beginit, auto& currit, auto& endit) {
+    ///             return currit->at(_2) + 20.0;
+    ///         });
+    ///     //   | height | depth |   month | length 
+    ///     // __|________|_______|_________|________
+    ///     //  0|   21.0 |  11.0 | 2022-01 |      1 
+    ///     //  1|   22.0 |  12.0 | 2022-02 |      2 
+    ///     //  2|   23.0 |  13.0 | 2022-03 |      3 
+    ///
     template<typename T, typename Ex>
     frame<T, Ts...>
     prepend_column(const std::string& column_name, Ex expr) const;