try and catch prob

Question

Luis Eduardo Cofré Lizama 2019-1-9

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/438851-try-and-catch-prob

评论： Walter Roberson 2019-1-9

Hi All, I am trying to read column headers in a file, however, sometimes the header varies by adding "_L" or "_R" to the name. I want to identify the row where the headers are using try/catch so if one set of variable names doesnt work then I use the modified one as below. Unfortunately, this is not working. I am expecting to get the second "emgvar" if the first one gives me a mismatch error. Help please.

emgvar = {'Spare_1';'Spare_2';'CH3_GME_';'CH4_GME_';'CH5_RF_L';'CH6_RF_R';'CH7_VL_L';'CH8_VL_R';'CH9_HB_L';'CH10_HB_';'CH11_TA_';'CH12_TA_';'CH13_GL_';'CH14_GL_';'CH15_SOL';'CH16_SOL'};
for n = 1:length(data)
if ~isempty(strfind(data{n},emgvar{1,1}))
    E_rowNumber = n;
    E_rowData = data{n};
    splitRowData_E = regexp(E_rowData,'	','split');
    try
        for a = 1:length(emgvar (:,1))
            E_loc (a,1) = find(ismember(splitRowData_E,emgvar {a,1}),1);
        end
    catch ME1
        idSegLast = regexp (ME1.identifier, '(?<=:)\w+$','match');
        
        if strcmp(idSegLast,'InvalidFid')
            emgvar = {'Spare_1';'Spare_2';'CH3_GME_L';'CH4_GME_R';'CH5_RF_L';'CH6_RF_R';'CH7_VL_L';'CH8_VL_R';'CH9_HB_L';'CH10_HB_R';'CH11_TA_L';'CH12_TA_R';'CH13_GL_L';'CH14_GL_R';'CH15_SOL_L';'CH16_SOL_R'};
        end
        try
            for a = 1:length(emgvar (:,1))
                E_loc (a,1) = find(ismember(splitRowData_E,emgvar {a,1}),1);
            end
        catch ME2
            fprintf('No data found');
        end
    end
end
end

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Answer 1

Walter Roberson 2019-1-9

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/438851-try-and-catch-prob#answer_355590

Why are you checking MATLAB:FileIO:InvalidFid ? That section of code is not reading a file.

If there are no elements matching that variable then the ismember() would return a vector that is completely false, and the find(,1) of that would return empty. You would then have an error from trying to assign emptiness to something. That would give you a MATLAB:subsassigndimmismatch error. Try/catch is a pretty heavy-handed way to do your checking.

I am a left uncertain in your code. Is each column individually subject to occur in base form or base_L form or base_R form ? Other than Spare_1 and Spare_2 ? Are CH3 through CH16 all required to appear, or can some be missing?

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Luis Eduardo Cofré Lizama 2019-1-9

yep, excactly same order, just "_L" and "_R" differ for some names (e.g. CH3_GME_ CH4_GME_ CH10_HB_ CH11_TA_ CH12_TA_ CH13_GL_ CH14_GL_ CH15_SOL CH16_SOL). It seems that characters length number got restricted to 7 in my new files and that's why I had the prob with my script.

regards

eduardo

Walter Roberson 2019-1-9

You know you can strcmpn() ? Though now I am wondering why you are bothering to do this checking, when it sounds like you could simply look for lines that start with Spare_1 and then assume that the columns are the correct purpose and the correct order.

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