Convert JSON to Table and Query Specific Value

2023 8 15
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更新时间：2023 8 16
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I have the following JSON array:
{"views":[{"Name":"A","Conf":"High","View":"Negative"}, {"Name":"B","Conf":"Low","View":"Negative"}, {"Name":"C","Conf":"Low","View":"Negative"}]}
How can I convert it to Table? Also, how can I query a specific row of the table? (Example: Find value of "Conf" where Name is "C.)
So far I have:
jsonData = '{"views":[{"Name":"A","Conf":"High","View":"Negative"}, {"Name":"B","Conf":"Low","View":"Negative"}, {"Name":"C","Conf":"Low","View":"Negative"}]}'
structData = jsondecode(jsonData);

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Florian Bidaud
Florian Bidaud 2023-8-15
编辑：Florian Bidaud 2023-8-15
Ran in:

1 个投票

Ran in:
jsonData = '{"views":[{"Name":"A","Conf":"High","View":"Negative"}, {"Name":"B","Conf":"Low","View":"Negative"}, {"Name":"C","Conf":"Low","View":"Negative"}]}'
jsonData = '{"views":[{"Name":"A","Conf":"High","View":"Negative"}, {"Name":"B","Conf":"Low","View":"Negative"}, {"Name":"C","Conf":"Low","View":"Negative"}]}'
structData = jsondecode(jsonData)
structData = struct with fields:
views: [3×1 struct]
structDataTable = struct2table(structData.views)
structDataTable = 3×3 table
Name Conf View _____ ________ ____________ {'A'} {'High'} {'Negative'} {'B'} {'Low' } {'Negative'} {'C'} {'Low' } {'Negative'}
structDataTable.Name
ans = 3×1 cell array
{'A'} {'B'} {'C'}
structDataTable.Conf{[structDataTable.Name{:}]=='C'}
ans = 'Low'

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Monkey Coder
Monkey Coder 2023-8-15
Thanks Florian . Can you please also suggest how to query specific row in the table/struct? Example : Find value of "Conf" where Name is "C.
Florian Bidaud
Florian Bidaud 2023-8-15
编辑：Florian Bidaud 2023-8-15
structDataTable.Conf{[structDataTable.Name{:}]=='C'}
Monkey Coder
Monkey Coder 2023-8-16
Can I please check how to query data for a string value? It works with 'C' but throw an error when I try the following code:
structDataTable.Conf{[structDataTable.Name{:}]=='Cat'};
Error: Matrix dimensions must agree.
Florian Bidaud
Florian Bidaud 2023-8-16
编辑：Florian Bidaud 2023-8-16
Ah yes sorry, you need to use strcmp as follows :
structDataTable.Conf{strcmp([structDataTable.Name(:)],'Cat')};
Monkey Coder
Monkey Coder 2023-8-16
Thanks, it works when there is a match. However, it throws an error when it cant find a match.
Error : Unable to perform assignment with 0 elements on the right-hand side.
How can I handle this?
Florian Bidaud
Florian Bidaud 2023-8-16
编辑：Florian Bidaud 2023-8-16
when you affect your value, first check if it's empty or not:
if ~isempty(structDataTable.Conf{strcmp([structDataTable.Name(:)],'Cat')})
value = structDataTable.Conf{strcmp([structDataTable.Name(:)],'Cat')};
else
value = nan;
end
Monkey Coder
Monkey Coder 2023-8-16
sorry, I am getting "Unable to perform assignment with 0 elements on the right-hand side." on the following line.
if ~isempty(structDataTable.Conf{strcmp([structDataTable.Name(:)],'Cat')})

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