How to extract table data based on column values?
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Answered: Struggling in MATLAB on 17 Mar 2022
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?
Eric Sofen on 17 Mar 2022
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.
More Answers (2)
Jon on 17 Mar 2022
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.
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