Hello, I have over 100,000 data points. I would like to do a scatter plot of
every 10th or 100th point. What is the best way to accomplish this task?

Kyle wrote:
Hello, I have over 100,000 data points. I would like to do a scatter plot of
every 10th or 100th point. What is the best way to accomplish this task?



You could copy the data to a separate range for charting. Use a formula
like

=MOD(ROW(),100)

then filter on the new formula column for any single value to see every
100th row, copy visible cells, paste elsewhere, and chart.

Kyle,

More meaningfully you should select the appropriate number of reduced
points, regardless of a changing number of original ones. This, in a
comfortable way, can be achieved by the following macro. You are free to add
mandatory prefices to variable names.

Option Explicit

Sub DataReduction()

'Petr Bezucha, 2008

'Subroutine reduces the count of xy data points to a set number
'and places the new range into the set position.
'Prerequisition is that the variables x and y
'should occupy the neighboring columns
Static PtsCount As Long
Dim DataCount As Long, DataStep As Long, S As Range, _
XO As Range, XR As Range, Inp As String, _
CO As Long, CR As Long, RO As Long, RR As Long, RM As Long
Const Title As String = "Data reduction"

'starting proposal
If PtsCount = 0 Then PtsCount = 50
'dispatching inputs
Set S = ActiveCell
On Error GoTo ErrExit
'cell selections are necessary
Set XO = Application.InputBox _
("Select the upmost X-original cell", _
Title, S.Address, , , , , 8)
Set XR = Application.InputBox _
("Select the upmost X-reduced cell", _
Title, S.Offset(, 2).Address, , , , , 8)
On Error GoTo 0

CO = XO.Column
CR = XR.Column
Inp = CStr(PtsCount)
Inp = Application.InputBox("Number of reduced points", _
Title, Inp, , , , , 1)
PtsCount = CLng(Inp)
Application.ScreenUpdating = False
RO = XO.Row
RR = XR.Row
DataCount = XO.End(xlDown).Row - RO + 1
DataStep = DataCount \ PtsCount
RM = XO.End(xlDown).Row - DataStep
Do While RO < RM
Cells(RO, CO).Copy Destination:=Cells(RR, CR)
Cells(RO, CO + 1).Copy Destination:=Cells(RR, CR + 1)
RO = RO + DataStep
RR = RR + 1
Loop
Application.ScreenUpdating = True
ErrExit:
End Sub

--
Petr Bezucha


"Kyle" wrote:

Hello, I have over 100,000 data points. I would like to do a scatter plot of
every 10th or 100th point. What is the best way to accomplish this task?