Using a loop to load multiple mat files from measurement into the workspace

Hello everyone,

it is my first time here.

My goal is to load a specific information out of around 20188 mat-files. Each file is a measurement-point. Each file includes two types of Informations. It is the surface and width of a area. I m only interested in the width. In the first picture you can see a Overview over the first five mat-files as the first five measurement points.The second picture here shows the structure of the first of the 20188 mat-files. In the picture the germen language is used. (width=max_Breite and surface=Flaeche, Measurement=Messung)

My code is here. The programm should write the parameter max_Breite in the array width. But because of the Ending .max_Breite he can't find the file.

width=[0];

for i=1:20188

switch i

case i<=9

width(i)=load(sprintf('Messung_0000%d.mat.max_Breite',i));

case i>=10 && i<100

width(i)=load(sprintf('Messung_000%d.mat.max_Breite',i));

case i>=100 && i<1000

width(i)=load(sprintf('Messung_00%d.mat.max_Breite',i));

case i>=1000 && i<10000

width(i)=load(sprintf('Messung_0%d.mat.max_Breite',i));

otherwise

width(i)=load(sprintf('Messung_%d.mat.max_Breite',i));

end

end

Error:

Error using load

Unable to read file 'Messung_00001.mat.max_Breite'. No such file or directory.

Error in Daten (line 22)

width(i)=load(sprintf('Messung_0000%d.mat.max_Breite',i));

Does somebody have a idear. I appreciate every kind of help and i m thankfull for everything. If you want you can write in german.

I thank you in advance

Erik

[Stephen23]

"But because of the Ending .max_Breite he can't find the file."

I don't see anything in the LOAD documentation that allows the filenames to be suffixed with names of variables inside the MAT file. Please show a link to the MATLAB documentation, which supports your attempted syntax.

If these are valid MAT files then LOADs output will be a scalar structure containing all of the imported data: why did you preallocate that array (misleadingly named WIDTH) with a scalar numeric?

Note that you can get rid of that complex SWITCH by simply specifying the fieldwidth in the SPRINTF format:

sprintf('Messung_%05d.mat',5)

ans = 'Messung_00005.mat'

sprintf('Messung_%05d.mat',543)

ans = 'Messung_00543.mat'

sprintf('Messung_%05d.mat',54321)

ans = 'Messung_54321.mat'

https://www.mathworks.com/help/matlab/ref/sprintf.html#btf_bfy-1_sep_shared-formatSpec

[Erik]

thank you very much, you helped me to improve my code. You are right, i deleted my initialization of the array width. With out the ending .max_Breite i could merge all files to one.

Answer 1

[Stephen23]

https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

P = '.'; % absolute or relative path to where the files are saved
S = dir(fullfile(P,'Messung_*.mat'));
for k = 1:numel(S)
    F = fullfile(P,S(k).name);
    D = load(F);
    S(k).width = D.max_Breite;
end
all_widths = vertcat(S.width)

The filenames and MAX_BREITE are stored in the structure array S. For example, the second file:

S(2).name
S(2).width