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acces data in struct

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Rica
Rica on 19 Jul 2019
Commented: Mario Chiappelli on 19 Jul 2019
Hi!
I have a struct Str. the element of the structure arle A, B, C,.... all of the are arrays with length 2000. I want to have onle the element from 500:1500 without writing
Str.A1=Str.A(500:1500) for every struct element.
is there an easy way to achieve this goal?
thank you!

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Accepted Answer

Peter Jarosi
Peter Jarosi on 19 Jul 2019
Edited: Peter Jarosi on 19 Jul 2019
You can use for loop indexing elements of your structure:
myElements = fieldnames(Str);
% or you can list your elements
% myElements = {'A', 'B', 'C'};
for x = 1 : length(myElements)
e1 = myElements{x};
e2 = strcat(e1, '1');
Str.(e1)=Str.(e2)(500:1500);
end
Please, let me know if it works for you

  2 Comments

Rica
Rica on 19 Jul 2019
it works! but you should change this:
e2 = strcat(e1);
Thank you!
Peter Jarosi
Peter Jarosi on 19 Jul 2019
You're very welcome!
You are right, if you want to overwrite your existing instances. In this case strcat() is even unnecessary:
myElements = fieldnames(Str);
% or you can list your elements
% myElements = {'A', 'B', 'C'};
for x = 1 : length(myElements)
e1 = myElements{x};
Str.(e1)=Str.(e1)(500:1500);
end
but in your question you wrote:
Str.A1=Str.A(500:1500);
that's why I thought that you want to create new elements of your structure in order to save old ones.

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More Answers (2)

Mario Chiappelli
Mario Chiappelli on 19 Jul 2019
Edited: Mario Chiappelli on 19 Jul 2019
I would loop through each A,B,C... Other languages call this a for each loop.
for str = {'A','B','C'}
variableName = strcat(str{1},'1');
Str.(variableName) = Str.(str{1})(500:1500);
end
Note: Instead of looping through numbers where each iteration is stored in the for statement variable "i" (or whatever you decide to call it), you are looping through each letter and the for statement variable in this case is "str".

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Show 3 older comments
Peter Jarosi
Peter Jarosi on 19 Jul 2019
It's a nice trick:
for str = {'A','B','C'}
but in this case doesn't work properly, because you will get 1x1 cells instead of strings. So you need one more step in order to convert them to strings, otherwise you won't be able to use them inside the parenthesis syntax.
Peter Jarosi
Peter Jarosi on 19 Jul 2019
Good job! I've given you a vote for it.
One little thing is left. Change "1" to '1'
Mario Chiappelli
Mario Chiappelli on 19 Jul 2019
*thumbs up emoji

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Rica
Rica on 19 Jul 2019
Thank you to every one!

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