Dynamically rename existing structure arrays

9 views (last 30 days)
Chiara Avancini
Chiara Avancini on 28 Jul 2014
Edited: Chiara Avancini on 28 Jul 2014
Hi all,
I have several .mat files, each of them containing one structure array named "data" (named exactly the same in each .mat file), like the following
data =
hdr: [1x1 struct]
label: {306x1 cell}
time: {1x25 cell}
and my ultimate aim is to merge all those "data" arrays using a function (ft_appendata) of the Fieldtrip toolbox.
In order to do that, I need to have all those "data" arrays named differently from each other.
What I want to do is to create a loop which loads the files and dynamically renames the "data" arrays.
For example, having the files...
1_myfile_1.mat
1_myfile_2.mat
2_myfile_1.mat
2_myfile_2.mat etc...
...I want to load all the files and rename each "data" variable contained in each .mat file...
for s=1:2
for r=1:2
load([num2str(s),'_myfile_',num2str(r),'.mat'])
%here piece of code, which I don't know, needed for renaming the variable
end
end
...in order to get something like...
1_data_1 =
hdr: [1x1 struct]
label: {306x1 cell}
time: {1x25 cell}
1_data_2 =
hdr: [1x1 struct]
label: {306x1 cell}
time: {1x19 cell}
2_data_1 =
hdr: [1x1 struct]
label: {306x1 cell}
time: {1x16 cell}
etc.
I tried to use the eval() function but, as far as I have understood, it generates from scratch a new variable dynamically changing name at each iteration, while I need to simply rename an already existing structure array.
Thank you in advance for your kind help, Chiara

Sign in to answer this question.

Accepted Answer

Image Analyst
Image Analyst on 28 Jul 2014
Edited: Image Analyst on 28 Jul 2014
Don't do that. Put them into an array instead.
% Read all data into different cells of a cell array
allData = cell(2, 2); % Initialize to whatever size you need
folder = pwd; % Current folder or wherever you want.
for s = 1 : size(allData, 2)
for r = 1 : size(allData, 1)
baseFileName = sprintf('%d_myfile_%d.mat', s, r);
fullFileName = fullfile(folder, baseFileName);
if exist(fullFileName, 'file')
storedStructure = load(fullFileName)
% Put into cell at row r, column s:
ca(r, s) = {storedStructure.data};
end
end
end
A structure array would also work. These methods are preferred over what you asked for. Why? Read the FAQ: http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F
  1 Comment
Chiara Avancini
Chiara Avancini on 28 Jul 2014
Edited: Chiara Avancini on 28 Jul 2014
Thank you! this worked nicely and it is also a pretty flexible solution for other types of data.

Sign in to comment.

More Answers (2)

Michael Haderlein
Michael Haderlein on 28 Jul 2014
It's not necessary to rename your variables. I suppose you want a matrix with all the structure, right? Then, the following should work:
alldata=struct('hdr',cell(2),'label',[],'time',[]);
for s=1:2
for r=1:2
load([num2str(s),'_myfile_',num2str(r),'.mat'])
alldata(s,r)=data;
end
end
dpb
dpb on 28 Jul 2014
Edited: dpb on 28 Jul 2014
Just concatenate them as you read the files...
alldat=[]; % an empty holder
for s=1:2
for r=1:2
alldat=[alldat;load([num2str(s),'_myfile_',num2str(r),'.mat'])]; % concatenate each
end
end
ADDENDUM
If don't have a huge number this shouldn't be too bad altho it's generally not "best practice" to dynamically grow arrays. Not sure w/ structures what happens if create an empty structure array vis a vis concatenation; never tested it.

Categories

Find more on Structures in Help Center and File Exchange

Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!