Even though quite easy to understand and use,

*TransformRowsDic()*

^{1}in the free .net library finaquant® protos is one of the most versatile and useful table transformation functions. This table function offers a simple way for applying user-defined formulas on each row of a table.

Using this row transformer you can:

- derive the value of a field of a table in terms of other related fields.
- apply logical and mathematical operations on some fields of table.

Following examples illustrate how *TransformRowsDic()* can be used in practice for the purposes listed above. All the examples start with the *TestTable* below as the primary input parameter^{2}.

## Example 1: Calculating related key figure “price” for each row

This example illustrates how the values of a new key figure *price* is assigned with the user defined formula:

price = (1 + margin_percentage) x costs

// see user-defined function UserFunctions.CalculatePriceDic_1() // KeyFigDic["price"] = (1 + KeyFigDic["margin_percentage"]) * KeyFigDic["costs"]; // insert new key figure "price" into table OutputTbl = MatrixTable.InsertNewColumn(TestTable, "price", 0.0); // transform rows OutputTbl = MatrixTable.TransformRowsDic(OutputTbl, UserFunctions.CalculatePriceDic_1); // view output table MatrixTable.View_MatrixTable(OutputTbl, "CASE 1: price = (1 + margin_percentage) x costs"); |

User-defined function CalculatePriceDic_1() as delegate function input to row transformer TransformRowsDic:

// User-defined function for transforming rows (row-by-row processing) // price = (1 + margin_percentage) * costs public static void CalculatePriceDic_1( ref Dictionary<string, string> TextAttribDic, ref Dictionary<string, int> NumAttribDic, ref Dictionary<string, double> KeyFigDic) { // user-defined formula for price KeyFigDic["price"] = (1 + KeyFigDic["margin_percentage"]) * KeyFigDic["costs"]; } |

Though it may seem complicated at first sight, the whole user-defined function above is nothing other than an envelope for the formula:

KeyFigDic["price"] = (1 + KeyFigDic["margin_percentage"]) * KeyFigDic["costs"]; |

## Example 2: Calculating “price” with conditional logic

In this example, the formula to be applied for calculating *price* depends on *product*:

price = (1 + margin_percentage) x costs, for products "Printer" and "Notebook" price = margin_fix + costs, for product "Camera"

// insert new key figure "price" into table OutputTbl = MatrixTable.InsertNewColumn(TestTable, "price", 0.0); // transform rows OutputTbl = MatrixTable.TransformRowsDic(OutputTbl, UserFunctions.CalculatePriceDic_2); // view output table MatrixTable.View_MatrixTable(OutputTbl, "CASE 2: Percentage price margin for \"Printer\" and \"Notebook\", additive margin for \"Camera\""); |

User defined function CalculatePriceDic_2() with conditional logic:

// - price = (1 + margin_percentage) x costs, for products "Printer" and "Notebook" // - price = margin_fix + costs, for product "Camera" // Note: price depends on some other key figures and text attribute "product" public static void CalculatePriceDic_2( ref Dictionary<string, string> TextAttribDic, ref Dictionary<string, int> NumAttribDic, ref Dictionary<string, double> KeyFigDic) { // user-defined conditional formula for price if (TextAttribDic["product"] == "Printer" || TextAttribDic["product"] == "Notebook") KeyFigDic["price"] = (1 + KeyFigDic["margin_percentage"]) * KeyFigDic["costs"]; if (TextAttribDic["product"] == "Camera") KeyFigDic["price"] = KeyFigDic["margin_fix"] + KeyFigDic["costs"]; } |

Note that the condition logic (i.e. which formula is to be applied for which products) is hard-coded in the example above. The following example shows, how the same problem could be solved in a more elegant way, by defining the *margin type* (fix or percentage) for each product as a table parameter.

## Example 3: Calculating “price” with a table parameter containing *margin type*

Beside implementing a more parametric and flexible approach compared to the second example above, this example also illustrates the practical use of combining tables in order to gather all relevant parameters in a single table.

A margin type for each product is defined in MarginTypeTable:

// combine TestTable and MarginTypeTable OutputTbl = MatrixTable.CombineTablesFirstMatch(TestTable, MarginTypeTable); // view combined table MatrixTable.View_MatrixTable(OutputTbl, "CASE 3: Combined table"); |

Now that we have all the relevant parameters including margin type in a single combined table, conditional formula for price can be applied on each row of table:

// insert new key figure "price" into table OutputTbl = MatrixTable.InsertNewColumn(OutputTbl, "price", 0.0); // transform rows OutputTbl = MatrixTable.TransformRowsDic(OutputTbl, UserFunctions.CalculatePriceDic_3); // view output table MatrixTable.View_MatrixTable(OutputTbl, "CASE 3: Price calculation with MarginTypeTable for determining margin types to be applied"); |

Written by: *Tunç Ali Kütükçüoglu*

- Transform rows of a table using dictionaries as associative arrays for keeping field names and values. [↩]
- These examples can be found as demo function in the Visual Studio project “FinaquantProtosStarter” which can be downloaded at the product page of finaquant® protos, in versions 1.02 and higher. [↩]