How to change the time increment of a text file to make a new data set from an existing one?

Question

Ryan Fishbaugh 2019-9-13

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https://ww2.mathworks.cn/matlabcentral/answers/480321-how-to-change-the-time-increment-of-a-text-file-to-make-a-new-data-set-from-an-existing-one

回答： Star Strider 2019-9-13

So I have a .txt file I want to load into another program, and before I do I want to change the time increment of the text file. So for example let's say I have a text file that looks like this:

where the first column is the time, the second is the x position, the third is the y position, and the fourth is the z position.

And I'm looking to finish with a code at a different increment, say instead of .1 it's point .06

Example
1 7 8 5
16 x2 y2 z2
22 x3 y3 z3
28 x4 y4 ...
34 ...
4  ...
46 ...

And make that the new data in the text file.

Anyone able to provide insight on how this might be done? Thank you.

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Answer 1

Star Strider 2019-9-13

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https://ww2.mathworks.cn/matlabcentral/answers/480321-how-to-change-the-time-increment-of-a-text-file-to-make-a-new-data-set-from-an-existing-one#answer_391789

在 MATLAB Online 中打开

Use interp1:

A = [1.1 7 8 5
     1.2 8 9 4
     1.3 9 10 3
     1.4 10 11 12
     1.5 11 12 1];
NewCol1 = min(A(:,1)) : 0.06 : max(A(:,1));
A2 = interp1(A(:,1), A(:,2:end), NewCol1(:));
NewA = [NewCol1(:) A2]

producing:

NewA =
1000    7.0000    8.0000    5.0000
1600    7.6000    8.6000    4.4000
2200    8.2000    9.2000    3.8000
2800    8.8000    9.8000    3.2000
3400    9.4000   10.4000    6.6000
4000   10.0000   11.0000   12.0000
4600   10.6000   11.6000    5.4000

However, if you later want to do signal processing on your re-timed matrix, the resample function is likely more appropriate. It incorporates an anti-aliasing filter.