Reading single value from text file

Question

Ted McG 2020-9-21

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https://ww2.mathworks.cn/matlabcentral/answers/597367-reading-single-value-from-text-file

回答： Ruger28 2020-9-21

Hello all,

I am reading in text files of the following format and would like to extract just the Peak frequency value (6.8 below) and put it into an array. What is the easiest way to do this? Thanks, fairly new to MATLAB.

Vibration Test

9/16/2020 2:12:25 PM

Sample Rate (Hz) = 2000.00

Peak frequency (Hz) = 6.8 Resolution (Hz) = 0.2

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Ruger28 2020-9-21

Will this sample be the only thing in each file? Meaning you might have 50 or so files that look just like this?

Ted McG 2020-9-21

yes

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Answer 1

Ameer Hamza 2020-9-21

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https://ww2.mathworks.cn/matlabcentral/answers/597367-reading-single-value-from-text-file#answer_498016

编辑：Ameer Hamza 2020-9-21

在 MATLAB Online 中打开

data.txt

Try this

str = fileread('data.txt');
peak_freq = regexp(str, 'Peak frequency \(Hz\) =[\s\t]*(\d*\.\d*)', 'tokens');
peak_freq = str2double(peak_freq{1}{1});

data.txt file is attached.

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Answer 2

Ruger28 2020-9-21

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https://ww2.mathworks.cn/matlabcentral/answers/597367-reading-single-value-from-text-file#answer_498022

在 MATLAB Online 中打开

One approach, which only works if these files dont change would be to read in and point to directly where the value is.

fname = 'C:\Users\<username>\Desktop\SampleFile.txt';
FID = fopen(fname);
x = textscan(FID,'%s');
fclose(FID);
freqVal = str2double(x{1,1}{15,1});

This looks directly at the location of the freq, that is if this file format never changes. Another method would be to use fgetl to extract each line, and search for your key terms, such as:

fname = 'C:\Users\<username>\Desktop\SampleFile.txt';
FID = fopen(fname);
loopcnt = 1;
while loopcnt
   temp = fgetl(FID);
   if any(strfind(temp,'Peak frequency (Hz) ='))
       startI = regexp(temp,'=','once');
       stopI = regexp(temp,'Resolution','once');
       Freq = str2double(strtrim(temp(startI+1:stopI-1)));
       break
   end
end
fclose(FID);