How to get particular data from column of table in MATLAB

i have this type of table. which is in the below image. and also upload the sample file which is "data.csv".

now I need only the row where this "LBNP:30" type of data is available in last column . please help. I am new to MATLAB.

[Stephen23]

@Dev Liya: we cannot test code on a screeshot. Please upload a sample file by clicking the paperclip button.

[Walter Roberson]

That is not a CSV file, and that is a problem you have to work around.

filename = 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/848860/data.csv';
outfile = fullfile(tempdir(), 'data.xlsx');
urlwrite(filename, outfile)

ans = '/tmp/data.xlsx'

cleanMe = onCleanup(@() delete(outfile));
T = readtable(outfile);
T.Var1(1:5)

ans = 5×1 cell array
    {'2021-11-01T19:59:49.706Z'}
    {'2021-11-01T19:59:49.707Z'}
    {'2021-11-01T19:59:50.041Z'}
    {'2021-11-01T19:59:50.043Z'}
    {'2021-11-01T19:59:50.044Z'}

T.Var1 = datetime(T.Var1, 'InputFormat', "yyyy-MM-dd'T'hh:mm:ss.SSS'Z'")

Error using datetime (line 651)
Unable to convert the text to datetime using the format 'yyyy-MM-dd'T'hh:mm:ss.SSS'Z''.

T(1:5,:)

[Walter Roberson]

@Dev Liya

Then you need to give the rule for which rows to select.

For example is the rule that you only want to select when the number after the colon is divisible by 10 ?

Is the rule that the third character of Var5 has to be in the second half of the alphabet ?

[Jan]

@Dev Liya: The nature of this forum is to share solutions. Therefore deleting questions, after they got answers, would be counterproductive. If you do have a good reason to remove the question, contact the admins. Please leave the question here otherwise. Thanks.

[Stephen23]

Original question retrieved from Google Cache:

https://web.archive.org/web/20220218181002/https://webcache.googleusercontent.com/search?q=cache%3Ah2ELEoDIS5kJ%3Ahttps%3A%2F%2Fwww.mathworks.com%2Fmatlabcentral%2Fanswers%2F1619680-how-to-get-particular-data-from-column-of-table-in-matlab

How to get particular data from column of table in MATLAB

i have this type of table. which is in the below image. and also upload the sample file which is "data.csv".

now I need only the row where this "LBNP:30" type of data is available in last column . please help. I am new to MATLAB.

[Rena Berman]

(Answers Dev) Restored edit

Answer 1

[Stephen23]

What you uploaded is not a CSV text file, it is an XLSX file with an incorrect file extension.

I fixed the file extension for you (attached).

T = readtable('data.xlsx')

T = 5×5 table
                Var1                   Var2       Var3    Var4        Var5    
    ____________________________    __________    ____    _____    ___________

    {'2021-11-01T19:59:49.706Z'}    1.5005e+07    113     32962    {'LBNP:30'}
    {'2021-11-01T19:59:49.707Z'}    1.5007e+07    114     32805    {0×0 char }
    {'2021-11-01T19:59:50.041Z'}     1.534e+07    115     32654    {'LBNP:40'}
    {'2021-11-01T19:59:50.043Z'}    1.5342e+07    116     32568    {'LBNP:50'}
    {'2021-11-01T19:59:50.044Z'}    1.5344e+07    117     32564    {0×0 char }

X = cellfun(@isempty,T.Var5);
T(X,:)= []

T = 3×5 table
                Var1                   Var2       Var3    Var4        Var5    
    ____________________________    __________    ____    _____    ___________

    {'2021-11-01T19:59:49.706Z'}    1.5005e+07    113     32962    {'LBNP:30'}
    {'2021-11-01T19:59:50.041Z'}     1.534e+07    115     32654    {'LBNP:40'}
    {'2021-11-01T19:59:50.043Z'}    1.5342e+07    116     32568    {'LBNP:50'}

[Stephen23]

"what is return cellfun to X ?"

X is a logical array the same size as T.Var5, with TRUE where the cells of T.Var5 are empty:

https://www.mathworks.com/help/matlab/ref/cellfun.html

"and what is the meaning of this line "T(X,:)= []" ?"

T(X,:)=[] uses logical indexing to remove every row of table T where X is TRUE.

Logical indexing is a very basic and important MATLAB concept:

https://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html

"i cannot understand it. specially "= []"."

That is a special syntax that removes elements from any array:

https://www.mathworks.com/help/matlab/math/removing-rows-or-columns-from-a-matrix.html

Answer 2

[Walter Roberson]

T = readtable('YourFileNameGoesHere.xlsx');
last_column = T{:,end};

[Walter Roberson]

T = readtable('YourFileNameGoesHere.xlsx');
mask = strcmp(T{:,end}, 'LBNP:30');
selected_rows = T(mask,:)

[Walter Roberson]

That is not a CSV file, and that is a problem you have to work around.

filename = 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/848860/data.csv';
outfile = fullfile(tempdir(), 'data.xlsx');
urlwrite(filename, outfile)

ans = '/tmp/data.xlsx'

cleanMe = onCleanup(@() delete(outfile));
T = readtable(outfile);
fmt = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";
T.Var1 = datetime(T.Var1, 'InputFormat', fmt, 'TimeZone', 'GMT', 'Format', fmt);
mask = strcmp(T{:,end}, 'LBNP:30');
selected_rows = T(mask,:)

selected_rows = 1×5 table
              Var1                 Var2       Var3    Var4        Var5    
    ________________________    __________    ____    _____    ___________

    2021-11-01T19:59:49.706Z    1.5005e+07    113     32962    {'LBNP:30'}

[Walter Roberson]

@Dev Liya

Although technically I could delete this answer, doing so would displease me. So.. NO.

[Walter Roberson]

@Dev Liya

If someone else is imposing on your a requirement to have this question deleted, then have them send a request to Mathworks to have it removed, along with an explanation of why it "must" be removed -- and also along with a plan to compensate the volunteers for their work. The volunteers do not agree to become free private consultants.