Iterating over Matlab struct

I have a 1x1 Matlab struct with 15 fields

results = 

     RAR_no_compartments_2_0: [1x1 struct]
     RAR_no_compartments_2_1: [1x1 struct]
    RAR_no_compartments_2_10: [1x1 struct]
    RAR_no_compartments_2_11: [1x1 struct]
    RAR_no_compartments_2_12: [1x1 struct]
    RAR_no_compartments_2_13: [1x1 struct]
    RAR_no_compartments_2_14: [1x1 struct]
     RAR_no_compartments_2_2: [1x1 struct]
     RAR_no_compartments_2_3: [1x1 struct]
     RAR_no_compartments_2_4: [1x1 struct]
     RAR_no_compartments_2_5: [1x1 struct]
     RAR_no_compartments_2_6: [1x1 struct]
     RAR_no_compartments_2_7: [1x1 struct]
     RAR_no_compartments_2_8: [1x1 struct]
     RAR_no_compartments_2_9: [1x1 struct]

I'm trying to cycle through each of these in a for loop:

model_names=fieldnames(results); %get the names of each sub-struct
fieldname_dims=size(fieldnames(results)); %get dimensions of each struct
for i=1:fieldname_dims(1), %iterate over number of substructs
    name=model_names(i) %get the model name
    results.(name) %access the substruct
end

However Matlab returns the following error:

Argument to dynamic structure reference must evaluate to a valid field name.

Could somebody please explain to me why this is an invalid field name?

Solution

This is precisely what structfun is made for. It allows you to loop through all the fields of a structure.

a = struct('a', 1, 'b', 2, 'c', 3);
structfun(@(x)disp(x), a)

1
2
3

Alternately, you may consider storing an array of structures rather than a structure where the fields have numbers in them like you have. Any time that you are reliant on a fieldname to know ordering, it may be better to use a different data structure.

For in your data, rather than having a fieldname of RAR_no_compartments_2_0 you'd simply assign the struct assigned to that field by index

RAR_no_compartments(1) = results.RAR_no_compartments_2_0;
RAR_no_compartments(2) = results.RAR_no_compartments_2_1;
...

This way, rather than a 1 x 1 struct with 15 fields, you'd have a 1 x 15 array of structs which is much easier to deal with natively within MATLAB.

Just a thought.