How can I make a structure array

Hello everyone,'

I want to make a struct array, or example "Spectra" or "freqs".

How can I implement it on my own (EEG)data?

Thanks in advance for your help.

Neda

Answer 1

[Walter Roberson]

If you pass struct() a cell array of data for a field, then it creates a struct array with the same size() as the size() of the cell array.

%setup to create cell arrays of data
N = 5;
spectras = arrayfun(@(n) randn(10,1), 1:N, 'uniform', 0);
freqs = arrayfun(@(n) sort(randi([0 999], 10, 1)), 1:N, 'uniform', 0);

%now that we have a cell arrays of data we can convert to struct array:

datastruct = struct('Spectra', spectras, 'freqs', freqs);

%verify that the struct is what we expect
whos datastruct

  Name            Size            Bytes  Class     Attributes

  datastruct      1x5              1968  struct              

datastruct

datastruct = 1×5 struct array with fields:
    Spectra
    freqs

datastruct(1).Spectra

ans = 10×1

0.7937 -0.6929 0.6557 -0.1090 -0.5371 -0.1283 -0.0640 -0.9109 1.6227 -1.6004

spectras{1}

ans = 10×1

0.7937 -0.6929 0.6557 -0.1090 -0.5371 -0.1283 -0.0640 -0.9109 1.6227 -1.6004

[Neda Deljavan]

Thanks for your answer.

What do you mean by "If you pass struct() a cell array of data for a field, then it creates a struct array with the same size() as the size() of the cell array."

[Walter Roberson]

Observe:

%setup to create cell arrays of data
N = 6;
spectras = arrayfun(@(n) randi([-9 9], 10,1), 1:N, 'uniform', 0);
freqs = arrayfun(@(n) sort(randi([0 999], 10, 1)), 1:N, 'uniform', 0);

%now that we have a cell arrays of data we can convert to struct array:

datastruct16 = struct('Spectra', reshape(spectras,1,6), 'freqs', reshape(freqs,1,6));
datastruct23 = struct('Spectra', reshape(spectras,2,3), 'freqs', reshape(freqs,2,3));

whos datastruct16 datastruct23

  Name              Size            Bytes  Class     Attributes

  datastruct16      1x6              2336  struct              
  datastruct23      2x3              2336  struct              

reshape(spectras,1,6) reshapes the 6-element cell array to be a 1 x 6 cell array. So for datastruct16 we passed in 1 x 6 cell arrays, and we got back a 1 x 6 struct array.

reshape(spectras,2,3) reshapes the 6-element cell array to be a 2 x 3 cell array. So for datastruct23 we passed in 2 x 3 cell arrays, and we got back a 2 x 3 struct array.

[Neda Deljavan]

Thanks a billion for your response.

I want to have "Spectra" and "freqs" like below.

[Walter Roberson]

t1 = cellfun(@squeeze, num2cell(spectra, 2), 'uniform', 0);
t2 = num2cell(freqs);
output = struct('spectra', t1(:) , 'freqs', t2(:) );