How can I extract arrays from a structure?

Question

Borja 2013-5-10

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Hi all,

This is my problem:

I load several files using the command 'dir'. Then, I import the data sheet (numbers + headers) with the command 'importdata'. The result is a structure (number of objects imported x 1).

The data are matrices of (602,603 or 604 x 9). I want to extract certain columns of the data sheets and I use a for loop but it gives this error:

Subscripted assignment dimension mismatch.

Error in loading (line 12)
Q(length(vals(i).data(:,7)),i)= vals(i).data(:,7)

Here I attach the piece of code:

clc;clear all;
% Loads the files of the selected directory
loadfiles = dir('*.txt');
% Preallocation of the variable which will contain the data
vals = [];
Q = [];
for i = 1:length(loadfiles)
  % Select the "useful" part of the structure (data)
  vals = [vals; importdata(loadfiles(i).name)];
  % Select the seventh column of each data sheet
  Q(length(vals(i).data(:,7)),i)= vals(i).data(:,7)
end

thanks in advance

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Answer 1

Alessandro Renna 2013-5-11

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编辑：Alessandro Renna 2013-5-11

在 MATLAB Online 中打开

try to use cell variable for Q as:

Q{length(vals(i).data(:,7)),i}= vals(i).data(:,7)

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Answer 2

Cedric 2013-5-12

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编辑：Cedric 2013-5-12

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There is no such thing as vals(i).data.

If you wanted to save only the 7 relevant columns, you could update a little your code as follows:

 cId = [1 2 3 4 6 7 9] ;                        % ID of the 7 relevant columns.
 Q   = [] ;
 for i  = 1 : length(loadfiles)
    buffer = importdata(loadfiles(i).name) ;    % Temporary storage.
    Q = [Q; buffer.data(:,cId)] ;               % Append only 7 relevant cols.
 end