vectorizing a script with cellfun

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Richard
Richard 2012-4-13
I'm aiming to import data from various folder and text files into matlab.
clear all
main_folder = 'E:\data';
%Directory of data
TopFolder = dir(main_folder);
%exclude the first two cells as they are just pointers.
TopFolder = TopFolder(3:end);
TopFolder = struct2cell(TopFolder);
Name1 = TopFolder(1,:);
%obtain the name of each folder
dirListing = cellfun(@(x)dir(fullfile(main_folder,x,'*.txt')),Name1,'un',0);
Variables = cellfun(@(x)struct2cell(x),dirListing,'un',0);
FilesToRead = cellfun(@(x)x(1,:),Variables,'un',0);
%obtain the name of each text file in each folder
This provides the name for each text file in each folder within 'main_folder'. I am now trying to load the data without using a for loop (I realise that for loops are sometimes faster in doing this but I'm aiming for a compact script).
The method I would use with a for loop would be:
for i = 1:length(FilesToRead);
data{i} = cellfun(@(x)dlmread(fullfile(main_folder,Name1{i},x)),FilesToRead{i},'un',0);
end
[~,Variable] = cellfun(@(x)fileparts(x),FilesToRead{1},'un',0);
Is there a method which would involve not using loops at all? something like cellfun within cellfun maybe? I also realise that textscan is better for importing text files, but dlmread works fine in this example.
In addition is it possible to create a variable in the workspace corresponding to 'Variable'?

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采纳的回答

Andrei Bobrov
Andrei Bobrov 2012-4-13
data = arrayfyn(@(ii)cellfun(@(x)dlmread(fullfile(main_folder,Name1{ii},x)),FilesToRead{ii},'un',0),1:length(FilesToRead),'un',0);

更多回答（2 个）

Sean de Wolski
Sean de Wolski 2012-4-13
It looks like you could wrap cellfun around that instead of a for-loop.
I'm obligated to remind you that well written for-loops will likely be faster and easier to read. I don't completely understand why you want to use 'compactness' as a metric for code quality. Most people will understand what two for-loops do. It takes someone with a fair amount of MATLAB experience to understand cellfun
Jan
Jan 2012-4-13
cellfun with anonymous functions is slow. I'm convinced, that a simple FOR-loop approach is faster - concerning programming, debug and runtime.
Omitting the first two entries of the reply of dir is not secure, because it is not documented, that . and .. are set to the front. Although I did not see them appear at another location, I use strcmp({TopFolder.name}, '.') to exclude these folders.
  2 个评论
Richard
Richard 2012-4-13
when would you suggest to avoid loops? also whatdo you mean by stating 'cellfun' with anonymous function?
Jan
Jan 2012-4-14
@lestyn:
cellfun(@fileparts, a, 'un', 0) is faster than
cellfun(@(x) fileparts(x), a, 'un', 0).
The later is CELLFUN with an anonymous function.

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