Retrive cell names from structure into a string vector

Hi

I have a structure that contains cell's inside. I would like to retrive the name of the cells into a vector, so I can make a for loop. This data is just for one year, and I have alot, where the dates change, so I cant just write the dates down since they are generated automaticly. The cell array inside each date is the same.

Dates = ['April_24_2018';'May_01_2018';'May_08_2018'... %And so on.]

for h = 1:size(Dates,1)
Data = Input.Dates(h,:){1,2}(1,1);)
end

Can't find a guide to do this, can somebody help :) ?

Best Regards Mikkel

[Jan]

To be exact: You want the names of the fields and not of the cells. Cells do not have names.

[Mikkel]

Hi Jan

How do I make a code that can access the Input.April_24_2018{1,3}(1,1) without having to write the April_24_2018 ? I would like to have something like. Input.(1){1,3}(1,1)...

[Stephen23]

@Mikkel: awkwardly forcing meta-data into fieldnames is not likely to make your code very neat or efficient. A non-scalar structure would make it trivially easy to loop over the elements, using basic indexing:

S(1).time = [2019,02,12];
S(1).data = {...};
S(2).time = [2019,02,12];
S(2).data = {...};
...
for k = 1:numel(S)
    S(k).time
    S(k).data{1}(1)
end

https://www.mathworks.com/help/matlab/matlab_prog/access-multiple-elements-of-a-nonscalar-struct-array.html

Answer 1

[Adam Danz]

See fieldnames()

https://www.mathworks.com/help/matlab/ref/fieldnames.html

[Mikkel]

Hi

Yeah it gets the names but how can I use that in a for loop?

If I do this:

fields = fieldnames(Input)

It gives me the names into at cell, but i cant:

for h = 1:size(fields,1)
    Input.fields{1,h}{1,2}(1,1)
end

I get the error:

Reference to non-existent field 'fields'.

I dont know if im going at it the right way? Is there a better and smarter way?

[Jan]

Input.(fields{1,h}){1,2}(1,1)
%     ^           ^   Important parentheses

[Steven Lord]

Use dynamic field names.

Alternately if you just want to iterate through the fields in the struct array consider using structfun.

[Adam Danz]

@Mikkel, now that your question has become clearer, you've got some decisions to make.

Using a non-scalar structure would really clean things up (as suggested by Stephen Cobeldick). You could convert your existing data to this format or, if possible, you could change the existing code that generated the structure in the first place.

If you decide not to go that route, two good options are structfun at dynamic field names (as suggested by Jan and Steven Lord. If you're just applying the same function to all fields and all of your fields are organized in the same way, go with structfun(). Otherwise, go with dynamic field names (or a combination of both).

If you get stuck, feel free to follow-up. Providing a sample of data always helps.