Getting directly range of value from MATLAB table?

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George Ghimire 2020-10-8

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评论： Star Strider 2020-10-8

Hi Everyone

Consider I have a MATLAB table which contains a frequency value from 1 Hz to 1000 Khz. From here I want to take only data between 300 Khz to 400 Khz. I donot want to use indexing . Is there anything i can do to extract directly the values ranging from 300 Khz to 400 Khz.

My f should have value like this in script (without indexing)

f = 300 Khz to 400 Khz

Thanks

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Answer 1

Star Strider 2020-10-8

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Try this:

Freq = 1:10:1E+6;                                                   % Create Frequencies
Amplitude = randn(size(Freq(:))) +1j*randn(size(Freq(:)));          % Create Amplitude (Or Whatever The Rest Of The Table Contains)
T1 = table(Freq(:),Amplitude);                                      % Create Table
A1 = table2array(T1);                                               % Extract Data Array (Eaiser To Work With Here)
FreqRange = (300:400)*1E+3;                                         % Define As 300kHz - 400kHz
F300_400 = interp1(A1(:,1),A1(:,2), FreqRange).';                   % Use Interpolation To Extract Desired Data —> No Indexing!
T2 = table(FreqRange(:), F300_400);                                 % New Table (If Desired)

.

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George Ghimire 2020-10-8

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Hi Star Its quite good example you gave. But you have taken frequency as an input and exported the data which are in 300-400 Khz. But in my case frequency is one of my output which is inside the table and i want directly taking its range if possible

Star Strider 2020-10-8

Thank you!

I realise that you want frequency as an output.

In my code, the result ‘T2’ uses frequency (as ‘FreqRange’) as the first column, and the other values, as ‘F300_4100’ as the second (or more) columns.

All the information for that frequency range is in ‘T2’, including the frequencies.

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Answer 2

Jon 2020-10-8

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编辑：Jon 2020-10-8

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I'm not sure what you mean by not using indexing. In case this helps here is one way to do it. Suppose you have a table T, with columns f (in Hz) and x for the frequency and corresponding data values resp

f = T.f(T.f >= 300e3 & T.f <= 400e3)
x = T.x(T.f >= 300e3 & T.f <= 400e3)

or somewhat more efficiently:

idl = T.f >= 300e3 & T.f <= 400e3
f = T.f(idl)
x = T.x(idl)

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Jon 2020-10-8

编辑：Jon 2020-10-8

Obviously my answer uses indexing, which perhaps is counter to what you asked. I'm just wondering why you would not want to use indexing. What, if anything, would be the problem for you in doing it as I suggest. It seems quite simple, but maybe I am missing something.

George Ghimire 2020-10-8

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I am not preferring indexing because my table has many sub division and sub sub division inside, At the end i have around 5200 frequency data and i need to extract them in different range for different calculation. Thats why i want direct taking of frequency values

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