Discover MakerZone

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn more

Discover what MATLAB® can do for your career.

Opportunities for recent engineering grads.

Apply Today

To resolve issues starting MATLAB on Mac OS X 10.10 (Yosemite) visit: http://www.mathworks.com/matlabcentral/answers/159016

Sorting and Saving a subset from the array

Asked by Niraj Poudel on 29 Dec 2012

Hi there,

I have imported data from Excel and now have a 240X3 cell array called 'num'.

Once sorted it looks something like this:

16 1232 56

16 3455 56

16 5443 76

16 1232 88

17 4545 65

17 3432 87

All I want to do is for to write a for loop to select all rows of the data which start with 16's and then save it as another array say num_1, then take another chunk that starts with 17's and save it as num_2..etc.

How can I compose a for loop to take care of that. I have tried different measures based on other questions here in matlab central but to no avail.

Any help will be appreciated.

Sincerely yours; Nj

0 Comments

Niraj Poudel

Products

2 Answers

Answer by Walter Roberson on 29 Dec 2012
unum = unique(num(:,1));
for K = 1 : length(unum)
  these_num = num(num == unum(K), :);
  num_{K} = these_num;
end

This will create num_{1}, num_{2} and so on. Creating actual new variables is not a good idea; see http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F

1 Comment

Niraj Poudel on 29 Dec 2012

Hi Walter, Thank you for your prompt response. However when I run the code you just sent me, it keeps telling me that the index exceeds matrix dimensions, plus I do not see anywhere in the code where I can specify the rows starting with 16 and 17 and so forth?

Am I missing something? Any help will be appreciated. Nj

Walter Roberson
Answer by Andrei Bobrov on 29 Dec 2012
Edited by Andrei Bobrov on 29 Dec 2012
a0 = {16 1232 56
16 3455 56
16 5443 76
16 1232 88
17 4545 65
17 3432 87};
a = cell2mat(a0);
[b,~,c] = unique(a(a(:,1)>=16,1));
num = ...
[num2cell(b),cellfun(@(x)a(x,2:3),accumarray(c,(1:numel(c))',[],@(x){x}),'un',0)];

2 Comments

Niraj Poudel on 29 Dec 2012

For some reason this does not work either. In this code there does not seem anywhere that rows starting with 16 should be saved as a different array? And 17 and 18 and so forth? I might be wrong. please correct me if I am so. Thank you for your response.

Andrei Bobrov on 29 Dec 2012

corrected

Andrei Bobrov

Contact us