MATLAB: Storing values in a structure - matlab

Question

Good day MATLAB pros,
I have a long list of (single value) variables in my workspace that has to be stored into an array for every loop of execution.
Here's a simple example:
Variables in the workspace:
a = 1;
b = 2.2;
c = 3.4;
d = [0.5 0.7 1 1.2 1.5];
e = [-15 -10 -5 0 5 10 15 20];
serial = {'WTZ00151'};
model = {'336F'};
NameList = {'a';'serial';'model'};
1) Here, I'm saving only the single value variables into Data structure, however what I'd like to do is for every loop, save the single values into an array in Data structure.
varList = who;
Data = struct;
fields = fieldnames(Data, '-full');
fieldSizes = structfun(#(field) length(field),Data);
% removing arrays from structure
for lst = 1:length(fieldSizes)
if fieldSizes(lst) > 1
Data = rmfield(Data,fields(lst));
end
end
Data =
Data: [1x1 struct]
a: 1
b: 2.2000
c: 3.4000
index: 10
model: {'336F'}
serial: {'WTZ00151'}
So if I run this in a loop, for i = 1:5, Data should look like this:
Data =
Data: [1x1 struct]
a: [1 1 1 1 1]
b: [1x5 double]
c: [1x5 double]
index: [10 10 10 10 10]
model: {1x5 cell}
serial: {1x5 cell}
Any ideas on how to code the for loop?
2) Since there are too many variables in the workspace & I have a long list of variables that needs storing, instead of using who to save ALL variables to the structure (and then filtering out the unwanted), how could I use a list of variable names (imported from a text file: NameList) to call out what needs to be stored? Using the variable name from NameList does not call out the structure values.
Much appreciated,

Answer 1

It's not immediately clear what part of your code actually is creating your data structure. There are several ways to create a struct from your array of variable names.
One way is to save the relevant variables to a file and load them back into a struct
save('tmp.mat', NameList{:});
Data = load('tmp.mat');
Another option (not recommended) is to use eval
for k = 1:numel(NameList)
Data.(NameList{k}) = eval(NameList{k});
end
As far as storing data from multiple iterations, I personally would recommend storing the data into an array of struct rather than a struct of arrays. You should be able to store each Data instance in an array using k as an index as shown below:
allData(k) = Data;
If you decide you really want a struct of arrays, you can always convert it afterwards.
fields = fieldnames(allData);
output = struct();
for k = 1:numel(fields)
% Try to just concatenate the values together
try
values = [allData.(fields{k})];
% If that failed, concatenate them within a cell array
catch
values = {allData.(fields{k})};
end
% Store this in a single output struct
output.(fields{k}) = values;
end