Undefined operator '==' for input arguments of type 'cell'.

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UMA RAMASAMY 2019-6-26

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/469002-undefined-operator-for-input-arguments-of-type-cell

评论： UMA RAMASAMY 2019-6-26

load hospital
hospital.Properties.ObsNames(1:10)
dsMale = hospital(hospital.Sex=='Male',:);
dsMale(1:10,{'LastName','Sex'})
this above code is present in matlab documentation this work well.... 
where as i tried in different dataset....
[~,~, AllData] =xlsread('play.xls','Sheet1','A1:E15');
student = cell2dataset(AllData);
ds1=student(student.class=='first',:)  % i need to store in another dataset student details who's class is first

i get an error...Undefined operator '==' for input arguments of type 'cell'.

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Answer 1

Guillaume 2019-6-26

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https://ww2.mathworks.cn/matlabcentral/answers/469002-undefined-operator-for-input-arguments-of-type-cell#answer_380908

在 MATLAB Online 中打开

Use strcmp to compare a cell array of char vectors to another char vector:

ds1 = student(strcmp(student.class, 'first'), :)

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Guillaume 2019-6-26

在 MATLAB Online 中打开

Sure, but as said for char arrays you can't use ==, you have to use strcmp, so:

student(strcmp(student.class, 'first') & student.mark >= 80, :)

If there is only a few different values in class, you could convert it to categorical, which uses == for comparison:

student.class = categorical(student.class);  %only needed once after loading the table
%...
student(student.class == 'first' & student.mark >= 80, :)  %class is categorical so can use ==

Alternatively, you can compare to a string (using "" instead of ''). strings also use == for comparison.

%optional, convert cell array of char vectors to string array
%student.class = string(student.class);
student(student.class == "first" & student.mark >= 80, :)  %string comparison. can use ==