How to extract table data based on column values?

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?

Answer 1

[Eric Sofen]

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.

[Atanu]

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.

Answer 2

[Jon]

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.

[Atanu]

Hi Jon! Thanks for your response. I have attached the in the original question.

Answer 3

[Atanu]

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',:);