How to extract table data based on column values?

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Struggling in MATLAB
回答： Struggling in MATLAB 2022-3-17
I have a table, part of which is displayed. I have attached the table in the question. The entries of the tables are 1*1 cell array.
I am trying to extract all the rows based on 'date'.
test_data((cell2mat(test_data.date) == '02/10/2022', :)
It gives me error "Row index exceeds table dimensions." I also get error for 'subjectid' or 'mazenumber' column.
But it works for "feeder" column.
>> test_data(cell2mat(test_data.feeder) == '4',:)
How do I fix this?

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采纳的回答

Eric Sofen
Eric Sofen 2022-3-17
One thing to watch out for is that the char vectors contained in the cell arrays (celltrs) can vary in the number of characters, causing cell2mat to fail. As @Jon suggested, strcmp between your char vector of interest and the cellstr variable is going to be much more robust.
Going a step further, it may make sense to convert some of your variables to more "modern" types:
subjectid - string
mazenumber - categorical
feeder - categorical or double
date - datetime
That said, depending on what you're doing with the data and how you're interacting with the database, it may not make sense to do the conversion.
  1 个评论
Struggling in MATLAB
Struggling in MATLAB 2022-3-17
编辑：Struggling in MATLAB 2022-3-17
Hi Eric! Thanks for your response. I have attached the in the original question. I tried using 'strcmp', But that did not work either. Both the elements I am comparing are 'char' vector.
>> cell2mat(test_data.mazenumber(1))
ans =
'maze 2'
>> class(cell2mat(test_data.mazenumber(1)))
ans =
'char'
>> class('maze 2')
ans =
'char'
>> test_data(strcmp(cell2mat(test_data.mazenumber),'maze 2',:));
Unrecognized function or variable 'strcmp'. % getting this error
I'll try to convert the variables now and see if that works.

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更多回答（2 个）

Jon
Jon 2022-3-17
Could be you should be using strcmp rather than == to compare the strings
It's a little hard to know exactly how you have the data stored in the table.
Please save your table using
save test_data.mat test_data
and attach the resulting test_data.mat so we can see what is going on.
Struggling in MATLAB
Thanks everyone for your comments. The problem is fixed now. I used the following code to get around.
test_data.date = datetime(test_data.date, 'InputFormat','MM/dd/yyyy');
all_trials_on_test_data = test_data((test_data.date) == '10-Feb-2022',:);

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