Iterate through a lot of Structs - matlab

Question

my Problem is the following:
I have about 300 Struct files given.
They are set up like this:
DSC_0001 has about 250 other struct files in it:
-> like this: DSC_0001.marker_1
And this one has 10 Numbers in it.
Like that:
DSC_0001.marker_1.flow_angle = 90
and now I want to iterate through all the Struct files
Something like that:
for i = 1:300
for j = 1:250
flow_angle = DSC_**i**.marker_**j**
end
end
Is there a way to do this?
I have the feeling that it could be really easy but I just can't find the solution...
I hope my question is clear enough...
Thanks for your help!

Answer 1

If possible don't use eval.
It depends on how your data is stored, but one possiblity is that it is in a .mat file. In that case it can be loaded using
DSC_structs = load('My_DSC_struct_file.mat');
and then you can access the values like so:
for i = 1:300
for j = 1:250
flow_angle(i,j) = DSC_structs.(['DSC_' sprintf('%04d',i)]).(['marker_' sprintf('%d',j)]);
end
end
Why avoid the eval function
Edit: You say that each struct is in a different file. That's a bit messier. I would probably do something like this to load them:
DSC_structs = cell(1,300);
for i = 1:300
%Note: I'm guess at your file names here
DSC_structs{i} = load(['DSC_' sprintf('%04d',i) '.mat'];
end
and then access the values as
DSC_structs{i}.(['DSC_' sprintf('%04d',i)]).(['marker_' sprintf('%d',j)]);

Answer 2

I guess this is a use case for the dreaded eval function:
for i = 1:300
for j = 1:250
eval (['flow_angle = DSC_', sprintf('%04d',i), '.marker_', num2str(j)]);
end
end
BUT NB there are 2 problems with my code above
You haven't told us where you want to store your angle, so my code doesn't :/ but you'd want something like this if you just want to store them in a matrix: eval (['flow_angle(', num2str(i), ',', num2str(j), ') = DSC_', sprintf('%04d',i), '.marker_', num2str(j)])
eval is a horrible way of doing things but you're forced to because someone saved your data in a horrible. Sort yourself out now for the future by re-saving your data in a smarter way! so something like:
.
for i = 1:300
eval ( ['DSC(', num2str(i), ') = DSC_', sprintf('%04d',i)]);
end
%// then save DCS!
And now your can iterate through this matrix of structs rather than having a 300 structs polluting your workspace and forcing you to use eval