acces data in struct

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!

Answer 1

[Peter Jarosi]

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

[Rica]

it works! but you should change this:

e2 = strcat(e1);

Thank you!

[Peter Jarosi]

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.

Answer 2

[Mario Chiappelli]

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".

[Peter Jarosi]

I think your code won't work, because, for instance you should use Str.(variableName) syntax instead of Str.variableName (and other problems).

[Mario Chiappelli]

What are these "other problems", you did exactly what I did but you put the parantheses around the variables.

[Peter Jarosi]

I didn't see your code when I was writing mine. You were just faster than me in order to submit it, and less accurate, and still having syntax errors. Test it first, before submit!

[Peter Jarosi]

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]

Good job! I've given you a vote for it.

One little thing is left. Change "1" to '1'

[Mario Chiappelli]

*thumbs up emoji

Answer 3

[Rica]

Thank you to every one!