How to access data in structures?

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Brett Baxter 2020-10-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/616618-how-to-access-data-in-structures

评论： Stephen23 2020-10-17

I'm currently learning how to use structures in MATLAB and I'm finding it a little more confusing than cells and other regular arrays. I'm confused on how to call data stored in specific fields of a structure. I understand the format is "nameofstructure"."nameoffield", but I'm struggling with how to get the data I need from the structure without knowing the name of the fields. Say I had a structure with 2 fields, how would I go about getting the infomation from either one without knowing the name of the field? I tried pulling the names of the fields in a function and using them like so

fieldnames = fieldnames(structure)
fieldInedd = fieldnames(2)
informationfromthisfield = structure.fieldIneed

But this doesn't give a field that matlab can recognize and draw data from. Could anyone help?

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Stephen23 2020-10-17

To access the structure fieldname dynamically you need the syntax given here:

https://www.mathworks.com/help/matlab/matlab_prog/generate-field-names-from-variables.html

and to access the contents of the cell array returned by fieldnames you need to use curly braces:

https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html

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Answer 1

Walter Roberson 2020-10-17

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/616618-how-to-access-data-in-structures#answer_516243

在 MATLAB Online 中打开

fieldnames = fieldnames(structure)
fieldInedd = fieldnames{2}
informationfromthisfield = structure.(fieldIneed)

Notice the () around the field name: it is important. This syntax is "dynamic field names".

This syntax of dot followed by a variable name or expression in () is also used for referencing table variables that are not valid MATLAB variable names.