Array parameter instead of Object in Excel Worksheet Function

[steveyjg]

This is my first post so I'm not sure if this should be in the .NET forum or the VB forum. Anyway I'm using VB .NET and trying to call the Percentile function. The function needs an Object as a parameter, but I'm trying to pass it an Array. Here's some of my code:

Imports Microsoft.Office.Interop.Excel

Dim worksheetFunction1 As WorksheetFunction

percentileValue = worksheetFunction1.Percentile(intenArray, inputPerValue)

I get the error System.NullReferenceException when trying to execute the Percentile function call.

Is this due to the array not being an Object data type? Is there a way to convert or cast the array (it's an array of Doubles) to an Excel Object data type or something the Percentile function will be ok with?

I'm pretty new to VB and programming in general. Any help will be appreciated.

[shweta123]

Hi,

You can send the array as an Object.So ,I think that must not be giving error.Are you using dynamic array? If so , it may generate Runtime exception
if not initialised.

[radcaesar]

How you pass the array to that method ?

The usual method is,

string[] weekDays = new string[] { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };

PrintArray(weekDays);

Print array is a user defined method.

[steveyjg]

How would I pass the array as an Object? Could you give me an example.

I'm pretty sure the array is initialized properly.

I'll post more of my code so you can see what's going on. I'm reading in a bitmap image, getting the brightness values of each pixel, and storing the values in an array of doubles. I then want to find a certain percentile value of the array. Rather than write my own percentile function I'm trying to use the Excel Worksheet Function. Then I make all pixels <= the percentile brightness black else all other pixels are made white.

 
Public Function posterizeImage(ByVal gImage As Bitmap) As Image
 
        Dim pImage As Bitmap = gImage
        'prep soon to be posterized image
 
        Dim wid As Integer = gImage.Width
        Dim hgt As Integer = gImage.Height
        Dim totalPixels As Integer = Math.BigMul(wid, hgt) 'could be a very large number
        Dim tempcolor As Color
        Dim intenArray(totalPixels - 1) As Double
        Dim counter As Integer = 0
 
        'new variables for Excel percentile function
        Dim inputPerValue As Double
        Dim percentileValue As Double
        Dim worksheetFunction1 As WorksheetFunction
 
        'fill array intenArray with brightness (intesity) values
        'brightness values range from 0 (black) to 1 (white)
        For x As Integer = 0 To wid - 1
            For y As Integer = 0 To hgt - 1
                tempcolor = gImage.GetPixel(x, y)
                intenArray(counter) = tempcolor.GetBrightness
                counter += 1
            Next
        Next
 
        'sort the array - I don't know if this is necessary for the Excel function
        intenArray.Sort(intenArray)
 
        'find percentile value - uses Excel percentile function
        inputPerValue = txtPerValue.Text / 100.00
 
        'Excel percentile function
        percentileValue = worksheetFunction1.Percentile(intenArray, inputPerValue)  
 
        For x As Integer = 0 To wid - 1
            For y As Integer = 0 To hgt - 1
                tempcolor = gImage.GetPixel(x, y)
                If tempcolor.GetBrightness <= percentileValue Then
                    pImage.SetPixel(x, y, Black)
                Else
                    pImage.SetPixel(x, y, White)
                End If
            Next
        Next
 
        Return pImage
End Function
 
 

[kenobewan]

Either intenArray or inputPerValue are null, write values to discover which and work backwards debugging from there.

[steveyjg]

Neither parameter is null. None of the elements in the array are null.

Here is the link to the Percentile method:
http://msdn2.microsoft.com/en-us/lib...le(VS.80).aspx

It asks for an Object and I'm giving it an array of doubles. I believe this is the problem. So what can I pass to the method so it will work?

Is there a way to make an array of Doubles as an array of Objects?

[shweta123]

Hi,

This is the way you can do it,

Dim intenarry() as Double
Redim intenarray(totalpixels-1)
WorksheetFunction1.Percentile(intenarray)


Percentile(Byval o1 as Object)
'Access object as an array
End Sub

[steveyjg]

ReDim didn't work as a workaround. I did figure it out finally though. Here is the different syntax that worked.

Found it at:
http://p2p.wrox.com/topic.asp?TOPIC_ID=41465

Dim xl As Object
xl = CreateObject("Excel.Application")

'rather than
'Dim worksheetFunction1 As WorksheetFunction

then use
percentileValue = xl.Percentile(intenArray, inputPerValue)

which works perfectly!