Hi,

 I want to calculate a standard deviation (stddev). Here is what I have done in vb.net and it give me an error...

Here is the code :

Dim calculateur As FunctionCalculator = New FunctionCalculator()

Dim x

Dim a(5) As Double

calculateur.Expression = "stddev(a)"

What is wrong with that ?

 thanks a lot,

 André_Mag

You need to use it in association with a chart series.

 e.g.

bar.Values.Name = "values"

bar.Add( 2 )

bar.Add( 3 )

bar.Add( 2 )

bar.Add( 3 )

calculateur.Arguments.Clear()

calculateur.Arguments.Add( bar.Values )

calculateur.Expression = "STDDEV( Values )"

x = calculateur.Calculate()

Hi again,

 I see, I have 2 more questions, the first one is how do you declare the series. Is it like "

Dim barC As New PointSeries "

 and my other question is when I run the program, I have an error message at the line

calculateur.Expression = "STDDEV( Values )"

 It says that value ": Invalid argument name: Values"

Thanks,

 André_Mag

This is because the parameter's first letter is uppercase (Values), and the name's one is lowercase (values), a mistake I made in the code snippet I provided earlier.

To declare the bar series, you need to do it the following way, using a type cast

Here is the code that works :

 Dim chart As Chart = ChartControl1.Charts(0)

Dim barSeries As BarSeries = CType(chart.Series.Add(SeriesType.Bar), BarSeries)

barSeries.Values.Name = "Values"

Dim calculateur As FunctionCalculator = New FunctionCalculator()

calculateur.Expression = "STDDEV( Values )"

Dim x = calculateur.Calculate()