printing the name of the data containing a certain value in the workspace

Question

yunus ay 2023-11-13

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2046750-printing-the-name-of-the-data-containing-a-certain-value-in-the-workspace

评论： yunus ay 2023-11-14

采纳的回答： Les Beckham

Hello, let's assume we have 5 data in the workspace.

a=10

b=20

c=30

d=40

reference=20

What I want to do is to take the difference of each value with the reference and determine the largest data from the reference.

So for example;

x1= a-ref

x2= b-ref

x3= c-ref

x4= d-ref

max_delta= max(x1,x2,x3,x4)

Winner = "d" --> I want a result like this. What formula should I use for this?

Thank you very much.

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Stephen23 2023-11-14

编辑：Stephen23 2023-11-14

在 MATLAB Online 中打开

"... but in my real project i have 896 .mat files and each mat file includes 9 column of different data. Data points in my question are reperesent the differetn mat files So for evaluate my all files, i guess i have to load all mat files and work from workspace seperately."

You guess incorrectly. A much better approach is to LOAD those MAT files into an output variable:

S = load(..)

and then access the fields of the structure S. Then easily store the data in arrays, just as MATLAB was written for. If you upload a sample file I could show you how. It really is much better than LOADing 896 MAT files directly into the workspace.

Hopefully all of those MAT file use exactly the same variable names, so your code will be simple and robust. If the names are different in every MAT file then ... go to the person who created them and tell them to fix their badly designed data.

Hopefully you are not going to sit and write out 896 variable names to join them into one vector.

Stephen23 2023-11-14

编辑：Stephen23 2023-11-14

在 MATLAB Online 中打开

demo.zip

"My files are in parquet format and unfortunately, although the naming is similar, each file has a different name. The numbers in the names change regularly."

The filenames are irrelevant. Read my previous comment: I was talking about variable names, not filenames.

Somehow you must have magically created lots of variables from those parquet files. Best avoided.

unzip demo.zip
dir
.                                     CHR_Heating_0_Cooling_40.parquet      CHR_Heating_10_Cooling_40.parquet     CHR_Heating_20_Cooling_40.parquet     CHR_Heating_neg10_Cooling_40.parquet  
..                                    CHR_Heating_0_Cooling_45.parquet      CHR_Heating_10_Cooling_45.parquet     CHR_Heating_20_Cooling_45.parquet     CHR_Heating_neg10_Cooling_45.parquet  
CHR_Heating_0_Cooling_30.parquet      CHR_Heating_10_Cooling_30.parquet     CHR_Heating_20_Cooling_30.parquet     CHR_Heating_neg10_Cooling_30.parquet  demo.zip                              
CHR_Heating_0_Cooling_35.parquet      CHR_Heating_10_Cooling_35.parquet     CHR_Heating_20_Cooling_35.parquet     CHR_Heating_neg10_Cooling_35.parquet  
P = '.'; % absolute or relative path to where the files are saved
S = dir(fullfile(P,'CHR*.parquet'));
for k = 1:numel(S)
    % Import file data:
    F = fullfile(S(k).folder,S(k).name);
    T = parquetread(F);
    % Extract heating and cooling:
    X = regexp(S(k).name,'(pos|neg)?\d+','match');
    V = str2double(regexprep(X,'neg','-'));
    T{:,'Heating'} = V(1);
    T{:,'Cooling'} = V(2);
    S(k).data = T;
end
% Concatenate all tables together to make the data much easier to work with:
T = vertcat(S.data)
T = 92438×13 table
     SOC       Tmax       Tmin      Current    Voltage    StationLoad    ChrUsableEng    TotalLossEng    LossDCREng    Duration     TAvg      Heating    Cooling
    ______    _______    _______    _______    _______    ___________    ____________    ____________    __________    ________    _______    _______    _______

        20        -20        -20         0     377.97             0               0               0               0        0           -20       0         30   
    20.004    -19.913    -19.999    32.822     384.88      0.005224       0.0032292       0.0019948      5.0371e-05        1       -19.999       0         30   
    20.008     -19.77    -19.998    32.824     384.94      0.010678       0.0066754       0.0040025      0.00011358        2       -19.998       0         30   
    20.012     -19.62    -19.998    32.826     384.99      0.016132        0.010122       0.0060106      0.00017727        3       -19.998       0         30   
    20.016     -19.47    -19.997    32.828     385.04      0.021588        0.013568       0.0080192      0.00024139        4       -19.997       0         30   
     20.02     -19.32    -19.996     32.83     385.09      0.027044        0.017015        0.010028      0.00030592        5       -19.996       0         30   
    20.025     -19.17    -19.995    32.832     385.13        0.0325        0.020463        0.012038      0.00037084        6       -19.995       0         30   
    20.029    -19.022    -19.994    32.834     385.18      0.037957         0.02391        0.014047      0.00043611        7       -19.994       0         30   
    20.033    -18.873    -19.993    32.837     385.22      0.043415        0.027358        0.016057      0.00050173        8       -19.993       0         30   
    20.037    -18.726    -19.993    32.839     385.25      0.048874        0.030806        0.018068      0.00056766        9       -19.992       0         30   
    20.041    -18.579    -19.992    32.841     385.29      0.054332        0.034254        0.020078       0.0006339       10       -19.991       0         30   
    20.045    -18.432    -19.991    32.843     385.33      0.059792        0.037703        0.022089      0.00070043       11        -19.99       0         30   
    20.049    -18.286     -19.99    32.845     385.36      0.065252        0.041151        0.024101      0.00076723       12       -19.989       0         30   
    20.054    -18.141    -19.989    32.847     385.39      0.070713        0.044601        0.026112      0.00083431       13       -19.988       0         30   
    20.058    -17.996    -19.989    32.849     385.42      0.076174         0.04805        0.028124      0.00090163       14       -19.987       0         30   
    20.062    -17.851    -19.988    32.851     385.45      0.081635        0.051499        0.030136       0.0009692       15       -19.986       0         30   

Now you can easily use the inbuilt tools for processing your data, e.g.:

https://www.mathworks.com/help/matlab/matlab_prog/split-data-into-groups-and-calculate-statistics.html

https://www.mathworks.com/help/matlab/matlab_prog/perform-calculations-by-group-in-table.html

format compact
summary(T)
Variables:
    SOC: 92438×1 single
        Values:
            Min            20 
            Median     46.592 
            Max        80.023 
    Tmax: 92438×1 single
        Values:
            Min           -20 
            Median     15.907 
            Max        34.224 
    Tmin: 92438×1 single
        Values:
            Min           -20 
            Median    -3.2488 
            Max        14.606 
    Current: 92438×1 single
        Values:
            Min             0 
            Median     85.415 
            Max        133.49 
    Voltage: 92438×1 single
        Values:
            Min        377.97 
            Median      411.5 
            Max        442.54 
    StationLoad: 92438×1 single
        Values:
            Min             0 
            Median     28.142 
            Max        64.612 
    ChrUsableEng: 92438×1 single
        Values:
            Min             0 
            Median     22.694 
            Max        53.152 
    TotalLossEng: 92438×1 single
        Values:
            Min             0 
            Median       4.44 
            Max        11.468 
    LossDCREng: 92438×1 single
        Values:
            Min             0 
            Median    0.75362 
            Max        1.7878 
    Duration: 92438×1 single
        Values:
            Min            0  
            Median      2888  
            Max         7692  
    TAvg: 92438×1 single
        Values:
            Min           -20 
            Median     10.426 
            Max        31.779 
    Heating: 92438×1 double
        Values:
            Min         -10   
            Median        0   
            Max          20   
    Cooling: 92438×1 double
        Values:
            Min          30   
            Median       40   
            Max          45   

If you really want to process the data from just one file then you can do that too, either by filtering the table T or by accessing the data in structure S, e.g. for the 2nd file:

S(2).name % filename
S(2).data % filedata

https://www.mathworks.com/help/matlab/matlab_prog/access-multiple-elements-of-a-nonscalar-struct-array.html

yunus ay 2023-11-14

This for loop is definitely amazing for me. Solved my many others problem too.

For example, I will compare my Station Load column in each of my 896 files with each other.

I can do this more practically with the S file structure. Thank you very much

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Answer 1

Les Beckham 2023-11-13

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2046750-printing-the-name-of-the-data-containing-a-certain-value-in-the-workspace#answer_1351745

在 MATLAB Online 中打开

a=10;
b=20;
c=30;
d=40;
reference=20;
names = ["a", "b", "c", "d"];
[max_delta, idx] = max([a b c d] - reference);
fprintf('The largest difference from the reference is %d, for variable %s\n', max_delta, names(idx));
The largest difference from the reference is 20, for variable d

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yunus ay 2023-11-13

Yes that works. Thank you so much

Les Beckham 2023-11-13

@yunus ay

You are quite welcome.

Stephen23 makes a good point. It is generally easier to operate on data in vectors and/or matrices than in a bunch of different variables. Note that I created a vector out of your separate variables in order to find the max delta.

If this answer answers your question, please Accept it. Thanks.

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printing the name of the data containing a certain value in the workspace

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