Array operation--Offset value

[oly]

Hi all,

I would like to offset my DAQ data. Could any one of you help me on this? Thank you.

2D array is my DAQ data 

1 1 1 1 1

2 2 2 2 2

3 3 3 3 3

4 4 4 4 4

I would like average the first 5 data points as offset values. I finished this part and I got 1D offset array

1

2

3

4

The function I would like to relize is to minus the offset values from the data array. 

1 1 1 1 1                   1 1 1 1 1

2 2 2 2 2                   2 2 2 2 2

3 3 3 3 3      Minus     3 3 3 3 3

4 4 4 4 4                   4 4 4 4 4 

Is this possible, should  I expand the 1D array to  2D array before do the calculation? Thanks.

[altenbach · Accepted solution]

Get the first column then subtract it from the 2D array.

Easiest done when transposed because of autoindexing behavior. Here's an example. 

 

Message Edited by altenbach on 01-25-2010 09:28 AM

[Ray.R]

I don't understand what you are trying to do..

What do you mean about the offset values?

If you take the average of the first row:

1

2

3

4

You get 2.5.

Do you want to reduce the 2D array by a value of 2.5?

so you get...

-1.5

-0.5

0.5

1.5

When you say:  

1 1 1 1 1                   1 1 1 1 1

2 2 2 2 2                   2 2 2 2 2

3 3 3 3 3      Minus     3 3 3 3 3

4 4 4 4 4                   4 4 4 4 4

 

Is it a one-to-one relationship ie Array1[i,0] - Array2[i,j], which would give you:

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

???

EDIT SECTION:  was talking with a co-worker and finally hit the send button.

Just noticed Altenbach's answer... 

Message Edited by Ray.R on 01-25-2010 12:46 PM

[oly]

Thanks to all! I am trying to explain my question  a little bit more clear. 

As for offset value, for the example above,

1 1 1 1 1

2 2 2 2 2

3 3 3 3 3

4 4 4 4 4

I will take the first 5 data points and average them, let's say, for the first row, I got (1+1+1+1+1)/5=1. That is channel 1. For  the second row, I got (2+2+2+2+2)/5=2 for channel 2. 

Then I got a 1D offset array for 5 channels,

1 

2 

3
4

I already finished this part. 

Then I want every point in each channel minus this offset value.  For channel 1, offset value is 1, then I want every point 1,1,1,1,1 in the first row minus this offset value. so I will get 0 0 0 0 0 for the first row.

And the final array I got will be 

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0 

0 0 0 0 0

I am studying the program  alterbach gave. It seems to me that I need make some changes. Anyway,

Thank you!

[altenbach]

Well, it would really help to use example number that are less degenerate. 😉

Anyway, to take each row and subtract its mean, you could do the following:

 

Message Edited by altenbach on 01-25-2010 11:01 AM