MATLAB: Creating an array of structures

structures

Hey Community,

I am trying to solve a problem where I want to assign a field within a structure to another structure that contains a cell array of structures. For example, lets say I have some structure, pet.dog.type that I want to use to create another structure. For example dog.name1 = pet.dog.type{1}.name, dog.name2 = pet.dog.type{2}.name. Is there a way to create a structure in this way? When I try to do this I keep getting an error "unable to perform assignment because dot indexing is not supported for variables of this type."

Best Answer

When you say "pet.dog.type{1}.name," you're saying that one of the fields, "grand field" if you'd like rather than a child field, is actually a cell array. So if you did

ca = pet.dog.type{1};

you'd have a cell. ca would be a cell, NOT another structure. Cells cannot take fields. So you cannot do

v = ca.name;

because ca is a cell array and cell arrays do not take dot indexing - they have no field so they can't, it's impossible. So that's why you cannot say pet.dog.type{1}.name.

Related Solutions

MATLAB: Concatenate same fields in multiple structures in a loop using field names

Because all of the structures contain the same fieldnames they should be stored as one non-scalar structure:

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

>> S(1).one = [1,2];
>> S(1).two = NaN;
>> S(2).one = [3,4];
>> S(2).two = Inf;

Then the concatenation can be done in just a few lines:

>> C = struct2cell(S);
>> C = cellfun(@(c)[c{:}],num2cell(C,2:3),'uni',0);
>> Z = cell2struct(C,fieldnames(S),1);
>> Z.one
ans =
   1   2   3   4
>> Z.two
ans =
   NaN   Inf

EDIT: to load multiple mat files, where each contains one structure of unknown name:

for k = 1:numel(...)
    F = ... filename
    T = struct2cell(load(F));
    S(k) = T{1};
end

MATLAB: How to save every iteration into workspace

Use fullfile rather than string concatenation. To store the imported images in a loop simply preallocate a cell array before the loop, and then use indexing:

N = 170;
C = cell(1,N);
for k = 1:N
   name = fullfile(folder_name1,filesStruct1(c).name);
   alpha = double(dicomread(name1))*pi/4096 - pi/2
   dicomwrite(alpha, fullfile('Results',filesStruct1(c).name));
   C{k} = alpha;
end
save(mfilename,'C')

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

Best Answer

Related Solutions

MATLAB: Concatenate same fields in multiple structures in a loop using field names

MATLAB: How to save every iteration into workspace

Related Question