finding min and max values from a file

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Melissa Patterson 2011-6-17

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In a text file, I have a pressure listed. I am combining several files and I would like my program to find the highest pressure and lowest pressure. I think I use line=getl, but do not know how to format the line correctly, can you help me out?

Thank you!

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Answer 1

Fangjun Jiang 2011-6-17

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Please provide an example of your text file so we can help you. The task sounds not that hard. There are plenty of similar QAs regarding import text file for data. Once you get all the data, use min() and max() will get you the result.

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Melissa Patterson 2011-6-17

File_20psi.txt:

Pressure: 20 psi

FX: 1,2,3

FY: a,b

File_30psi.txt

Pressure: 30 psi

FX: 4,5,6

FY: c,d

File_40psi.txt

Pressure: 40 psi

FX: 7,8,9

FY: e,f

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Answer 2

Fangjun Jiang 2011-6-18

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在 MATLAB Online 中打开

Thank you for showing the example. I saw you posted similar questions a few times. Not sure how representative are these text files to your real data files. Your problem is trivial. The data format in your text file is irregular. You need to read the file and do specific string processing to get the data you want. I wrote the function below just show it can be done. But I suspect that it won't apply to your real data files. I hope you can use it as a starting point to get your task done.

Copy the following line to create ParseText.m file thus create the ParseText() function.

function [PR,FX,FY]=ParseText(TextFile)
fid=fopen(TextFile,'rt');
while ~feof(fid)
    TextLine=fgetl(fid);
    if strfind(TextLine,'Pressure:')
        PR=textscan(TextLine,'%s%f%s');
        PR=PR{2};
        continue;
    end
    if strfind(TextLine,'FX:')
        TextLine=strrep(TextLine,'FX:','');
        FX=textscan(TextLine,'%f','delimiter',',');
        FX=FX{1};
        continue;
    end
    if strfind(TextLine,'FY:')
        TextLine=strrep(TextLine,'FY:','');
        FY=textscan(TextLine,'%s','delimiter',',');
        FY=FY{1};
        continue;
    end
    disp('Un-recognized text line.');
end
fclose(fid);

Then run the following lines, assume you have the three text files as shown in your comment.

>> [PR.PR1,FX.FX1,FY.FY1]=ParseText('File_20psi.txt');
>> [PR.PR2,FX.FX2,FY.FY2]=ParseText('File_30psi.txt');
>> [PR.PR3,FX.FX3,FY.FY3]=ParseText('File_40psi.txt');
>> Pressure=[PR.PR1,PR.PR2,PR.PR3]
Pressure =
      20    30    40
>> FX_ALL=[FX.FX1;FX.FX2;FX.FX3]'
FX_ALL =
       1     2     3     4     5     6     7     8     9
>> FY_ALL=[FY.FY1;FY.FY2;FY.FY3]'
FY_ALL = 
      'a'    'b'    'c'    'd'    'e'    'f'
>> max(Pressure)
ans =
      40
>> min(Pressure)
ans =
      20

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Walter Roberson 2011-6-20

For example, use

[R20,X20,Y20] = ParseText('File_20psi.txt');

Fangjun Jiang 2011-6-20

Like Walter suggested, the code is for a M-function. You need to call it with an input argument 'File_20psi.txt', which is the name of the text file. The variable TextFile in the code will then has 'File_20psi.txt' as its value.

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