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{excerpt}The PowerPointTemplate object supports some basic formulas. Each of the formulas will perform a specific operation on the values referenced.{excerpt}  Formulas are evaluated for all values of the column in the data source, regardless of how many of the values are actually displayed in the document.

h2. To Use

The formula must follow the syntax {{%%=FORMULA_NAME(DataSource.ColumnName)}} where:
*  *FORMULA_NAME* is one of the formulas listed below \\ \*  *DataSourceName* is the name of the data source. This name is specified in code when the {{[PowerPointTemplate.BindData]}} method is called.  \\ \* *ColumnName* is the name of the column that contains the value(s) that will be used in the calculation. The column name must match the columns specified in code. 

There must be a call to {{PowerPointTemplate.BindData}} to bind a data source to the template, however, you do not need to include a full data marker (%%=DataSource.ColumnName) in the template to use the formula. 

h2. Supported Formulas

PowerPointWriter supports the following data marker formulas:
|| AVERAGE | Calculates the average of the column values ||
|| COUNT | Returns the number of values (that is, the number of rows in the data source) of the column ||
|| COUNTA | Returns the number of non-null values of the column ||
|| MAX | Returns the maximum value from the column ||
|| MIN | Returns the minimum value from the column ||
|| PRODUCT | Calculates the product of the column values ||
|| STDEV | Returns the standard deviation of the column values, treating the values as a sample ||
|| STDEVP | Returns the standard deviation of the column values, treating the values as a population ||
|| SUM | Calculates the sum of the column values ||
|| VAR | Returns the variance of the column values, treating the values as a sample ||
|| VARP | Returns the variance of the column values, treating the values as a population ||


{example}
h3. The Template

The example below uses formulas to display the average, standard deviation, maximum, and minimum college entrance exam scores of a group of fictional students as part of a table including their individual scores.  

!FormulaTemplate.png!

h3. The Code
The following code opens the template and binds data to it using the SetDataSource and SetRepeatBlock methods, then streams the resulting document to the user:

{code}
protected void AddFormulas(object sender, EventArgs e)
{
     PowerPointTemplate pptt = new PowerPointTemplate();
     pptt.Open("FormulaTemplate.pptx");
     
     //Get a Data Table of scores using the helper method
     DataTable ScoreData = GetScores();

     //Create DataBindingProperties
     DataBindingProperties dataBindProps = pptt.CreateDataBindingProperties();

     //Bind the data
     pptt.BindData(ScoreData, "Data", dataBindProps);
 
     pptt.Process();
     pptt.Save(Response, "ScoreReport.docx", false);
}

private DataTable GetScores()
{
     DataTable dt = new DataTable();

     dt.Columns.Add("StudentID", typeof(string));
     dt.Columns.Add("ReadingScore", typeof(int));
     dt.Columns.Add("WritingScore", typeof(int));
     dt.Columns.Add("MathScore", typeof(int));
     dt.Columns.Add("Score", typeof(int));

     Random rand = new Random();

     int rScore, wScore, mScore;
     for (int i = 0; i < 30; ++i)
     {
          rScore = rand.Next(400, 800);
          wScore = rand.Next(400, 800);
          mScore = rand.Next(400, 800);
          dt.Rows.Add(
               string.Format("S{0:000000}", rand.NextDouble() * 1000000),
               rScore, wScore, mScore, rScore + wScore + mScore
               );
     }

     DataTable dtSorted = dt.Clone();
     foreach (DataRow row in dt.Select("", "StudentID asc"))
          dtSorted.ImportRow(row);

     return dtSorted;
}
{code}

h3. Results
The formulas are evaluated by PowerPointTemplate, as you can see in the sample output slide:

!FormulaOutput.png!

{example}