| T O P I C R E V I E W |
| _convolution_ |
Posted - 02/15/2010 : 05:57:37 AM
Origin Ver. 8 SR0 and Service Release v8.0724:
Hello, I need to count the sum of my tabulated Y elements, shifting the frame of 100 elements along the X axis. How to do this? In the convolution dialog, it only suggests to enter two functions to be convoluted. What should I enter as a second function?
Thank you |
| 1 L A T E S T R E P L I E S (Newest First) |
| greg |
Posted - 02/16/2010 : 12:22:44 PM
It isn't clear to me that you want convolution. From your description, it sounds like you want a running sum or a group sum - depending on whether the sums overlap or not.
For non-overlapping group sums you can use Set Column Values:
Add a new column to your worksheet
Select the new column (click on it's name)
Right-click on the selection and choose Set Column Values
Enter a formula such as
N*ave(col(M),N)
where N is the group size (100 in your case) and M is the name or number of the column you seek to sum.
The ave( ) function calculates a group average based on group size:
ave(dataset,GroupSize)
You can get the sum rather than the average by multiplying by group size.
You can calculate a running sum by using the average command.
Two points regarding the average command:
(1) The command is destructive so apply to a copy of your data
(2) Group size is always odd, a point + N points before and after
So Set Column Values could again be used, but the script should be in the Before Formula Scripts section. For example:
col(C) = col(B); // Copy data so original is kept
average -n 50 col(C); // plus or minus 50 points
col(C) *= 101; // sum = ave * count which is 50 + 1 + 50
For an example of Convolution, you can import Samples\Signal Processing\Convolution.dat and see how the Signal data (collected from a noisy instrument) can be convoluted with Response data ( 'pure' gaussian) to removed noise and reveal the expected gaussian response. |
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