Index in position 2 exceeds array bounds. Index must not exceed 1 for ranksum looping

Hi, hope everyone have good day,

I'm trying to use ranksum for my coding because ranksum can use different length for x and y. but I keep receiving this problem.

Index in position 2 exceeds array bounds. Index must not exceed 1 and do not sure why and how to fix it because the p-value for ranksum appeared in the workspace.

thank you

AKIfolder = {'A003419.mat', 'A181069.mat', 'A929060.mat', 'B651999.mat', 'B664654.mat', 'B736322.mat', 'B764581.mat', 'B777509.mat', 'B780014.mat', 'B780227.mat'};

for AKI = 1:numel(AKIfolder)

listAKI = load(AKIfolder{AKI});

x = listAKI.PatientStruct.Greal(:,AKI);

end

SNAKIfolder = {'A030769.mat', 'A128207.mat', 'A138748.mat', 'A926245.mat', 'B238568.mat', 'B441119.mat', 'B496482.mat', 'B534716.mat', 'B773960.mat', 'B777504.mat'};

for SNAKI = 1:numel(SNAKIfolder)

listSNAKI = load(SNAKIfolder{SNAKI});

y = listSNAKI.PatientStruct.Greal(:,SNAKI);

end

[p] = ranksum(x,y);

[KSSV]

Which line is trhowing error? Copy and paste the full error lines here.

[farhah muhammad]

Error in pvalue (line 5)

x = listAKI.PatientStruct.Greal(:,AKI);

Error using dbcont

Debug commands only allowed when stopped in debug mode.

Answer 1

[Shivani]

Hi @farhah muhammad,

The error you are receiving is not because of the “ranksum” function. It is due to illegal memory access while indexing into the “GReal” array of the “PatientStruct”. However, the exact reason causing this error is difficult to determine without looking at the contents of the files in folder “AKIfolder” and “SNAKIfolder”.

I am assuming that you were trying to access all the rows in the GReal array for every file in the folder. As mentioned in the error, index in the second position cannot exceed 1, implying that there is only one column in the GReal array. Therefore, you can modify your code as shown below:

AKIfolder = {'A003419.mat', 'A181069.mat', 'A929060.mat', 'B651999.mat', 'B664654.mat', 'B736322.mat', 'B764581.mat', 'B777509.mat', 'B780014.mat', 'B780227.mat'}; 
x = []; 
for AKI = 1:numel(AKIfolder) 
    listAKI = load(AKIfolder{AKI}); 
    x = vertcat(x, listAKI.PatientStruct.Greal(:,1)); 
end 

SNAKIfolder = {'A030769.mat', 'A128207.mat', 'A138748.mat', 'A926245.mat', 'B238568.mat', 'B441119.mat', 'B496482.mat', 'B534716.mat', 'B773960.mat', 'B777504.mat'}; 
y = []; 
for SNAKI = 1:numel(SNAKIfolder) 
    listSNAKI = load(SNAKIfolder{SNAKI}); 
    y = vertcat(y, listSNAKI.PatientStruct.Greal(:,1)); 
end 

Note that I have also added an extra line of code that concatenates data extracted from all files in “AKIfolder" to “x” and data extracted from all files in “SNAKIfolder” to “y”. In the current version, “x” and “y” are being overwritten at every iteration, which ultimately defeats the purpose of the for loop.

Please refer to the link below for more information about indexing into a MATLAB array and the “vertcat” function:

• https://www.mathworks.com/help/matlab/math/array-indexing.html
• https://www.mathworks.com/help/matlab/ref/double.vertcat.html

I hope this resolves your issue!