Loading files by replacing some part of the name with a variable

Question

Simon Schirk 2023-12-4

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https://ww2.mathworks.cn/matlabcentral/answers/2056054-loading-files-by-replacing-some-part-of-the-name-with-a-variable

评论： Matt J 2023-12-4

Hi, I want to load a bunch of files in my workspace. There all name simmilarly and there's a number counting up, but its not just at the end of the Filename, so just replacing it with 'i' doesn't work.

Any ideas?

The 'i' in the file name are two digits. Starting with '01' and ending with '41'

I found a Video of someone explaining a similar issue, but I wasn't able to adapt the solution to my code.

for i = 01:41
FileName   = 'GNSS_Validierung_0i.mat';
FolderName = 'C:\Users\Admin\Documents\BA\MATLAB\Routenplanung\versuchsdaten_maxi';
File       = fullfile(FolderName, FileName);
load(File);   
x_DIY_flip = GNSS_Validierung_0i.Y(23).Data';
y_DIY_flip = GNSS_Validierung_0i.Y(25).Data';
x_ppm_flip = GNSS_Validierung_0i.Y(24).Data';
y_ppm_flip = GNSS_Validierung_0i.Y(26).Data';
.
.
.
end

2 个评论
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Stephen23 2023-12-4

编辑：Stephen23 2023-12-4

在 MATLAB Online 中打开

The MATLAB documentation shows you one approach using SPRINTF:

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

And then remember to always LOAD into an output variable:

S = load(..);

and then access its fields. Then you can avoid that major problem with magical dynamic variable names.

Dyuman Joshi 2023-12-4

Have a look at this - https://in.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

How do you get the data i.e. all the mat file, in the manner (using numbers in the name i.e. dynamically naming them) you have now? Is the data output from some code?

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Answer 1

Matt J 2023-12-4

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https://ww2.mathworks.cn/matlabcentral/answers/2056054-loading-files-by-replacing-some-part-of-the-name-with-a-variable#answer_1365274

编辑：Matt J 2023-12-4

在 MATLAB Online 中打开

Pre-generate all of the filenames and loop over them.

FileNames   = compose("GNSS_Validierung_%.2d",(1:41)' )
FileNames = 41×1 string array
    "GNSS_Validierung_01"
    "GNSS_Validierung_02"
    "GNSS_Validierung_03"
    "GNSS_Validierung_04"
    "GNSS_Validierung_05"
    "GNSS_Validierung_06"
    "GNSS_Validierung_07"
    "GNSS_Validierung_08"
    "GNSS_Validierung_09"
    "GNSS_Validierung_10"
    "GNSS_Validierung_11"
    "GNSS_Validierung_12"
    "GNSS_Validierung_13"
    "GNSS_Validierung_14"
    "GNSS_Validierung_15"
    "GNSS_Validierung_16"
    "GNSS_Validierung_17"
    "GNSS_Validierung_18"
    "GNSS_Validierung_19"
    "GNSS_Validierung_20"
    "GNSS_Validierung_21"
    "GNSS_Validierung_22"
    "GNSS_Validierung_23"
    "GNSS_Validierung_24"
    "GNSS_Validierung_25"
    "GNSS_Validierung_26"
    "GNSS_Validierung_27"
    "GNSS_Validierung_28"
    "GNSS_Validierung_29"
    "GNSS_Validierung_30"

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Stephen23 2023-12-4

编辑：Stephen23 2023-12-4

@Matt J: ah, I missed that dot indexing. Note that ".mat" is not valid in fieldnames.

Matt J 2023-12-4

@Stephen23 Good point. I've removed the .mat sub-string from the code I proposed (it was never necessary).

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Answer 2

Stephen23 2023-12-4

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编辑：Stephen23 2023-12-4

在 MATLAB Online 中打开

Do NOT name each variable dynamically. Unless you want to force yourself into writing slow, complex, inefficient, insecure, obfuscated code that is buggy and hard to debug.

Always LOAD into an output variable (which is a scalar structure). The your data-access problems are easily avoided:

P = 'C:\Users\Admin\Documents\BA\MATLAB\Routenplanung\versuchsdaten_maxi';
for k = 01:41
    F = sprintf('GNSS_Validierung_%02d.mat',k);
    C = struct2cell(load(fullfile(P,F));
    assert(isscalar(C),'Exactly one variable is allowed!')
    x_DIY_flip = C{1}.Y(23).Data.';
    y_DIY_flip = C{1}.Y(25).Data.';
    x_ppm_flip = C{1}.Y(24).Data.';
    y_ppm_flip = C{1}.Y(26).Data.';
    .
    .
    .
end

Note that your code would be simpler, more efficient, and much more robust if the variable names were exactly the same in every MAT file. That is to say, the data you have been given is badly designed.