Index through datestring, selecting whole hours

Hi,

i have the following problem. I have created a cell array consisting of two columns date and value, which looks like this (extract):

    '02-10-2014 20:30'    [10934]
    '02-10-2014 21:00'    [10195]
    '02-10-2014 21:30'    [ 9388]
    '02-10-2014 22:00'    [ 8808]
    '02-10-2014 22:30'    [ 8730]

I want to filter through the array and select only values that correspond to whole hours like:

   '02-10-2014 21:00'    [10195]
   '02-10-2014 22:00'    [ 8808]

Any suggestion please?

Many thanks

Stefan

Answer 1

[Azzi Abdelmalek]

 a={'02-10-2014 20:30'    [10934]
    '02-10-2014 21:00'    [10195]
    '02-10-2014 21:30'    [ 9388]
    '02-10-2014 22:00'    [ 8808]
    '02-10-2014 22:30'    [ 8730]}
c1=datevec(a(:,1),'dd-mm-yyyy HH:MM')
idx=c1(:,5)==0
out=a(idx,:)

[Stefan Hristov]

Many thanks Azzi,

that worked just fine! Actually i tried just datevec(a(;,1)) withoug assigning the format and it worked fine as well.

Best

Stefan

Answer 2

[Image Analyst]

Something like

counter = 1;
for row = 1 : size(ca, 1)
  cellContents = ca{row, 1}; % Extract first column of this row.
  if strfind(cellContents, ':00')
    % Cell contains :00, so append it to the output cell array.
    output_ca{counter, 1} = cellContents;
    output_ca(counter, 2) = ca(row, 2);
    counter = counter + 1;
  end
end

That's one way at least, sort of the intuitive but brute force way. There are probably other ways that are more compact, like using cellfunc() or something. Note how I used braces and parentheses. If you don't know why, see the FAQ : http://matlab.wikia.com/wiki/FAQ#What_is_a_cell_array.3F. You may find it easier to use a structure array than a cell array.

Answer 3

[Andrei Bobrov]

Z = {'02-10-2014 20:30'    [10934]
    '02-10-2014 21:00'    [10195]
    '02-10-2014 21:30'    [ 9388]
    '02-10-2014 22:00'    [ 8808]
    '02-10-2014 22:30'    [ 8730]};

[~,~,~,~,m] = datevec(Z(:,1),'dd-mm-yyyy HH:MM');
out = Z(m == 0,:);

or

out = Z(~cellfun('isempty',regexp(Z(:,1),':00')),:);

Answer 4

[Matz Johansson Bergström]

Another alternative where I just pick the last two characters from the first column of the cell:

%mock data:
cel{1,1} = '02-10-2014 21:00'; cel{1,2} = 3.2; 
cel{2,1} = '02-10-2014 21:03'; cel{2,2} = 7.2;
mask = cellfun(@(x) strcmp(x(end-1:end), '00'), cel(:,1))

>> cel(mask,:)
ans = 
    '02-10-2014 21:00'    [3.2000]

If you want to find out how many entries that are on the hour:

sum(mask)

Answer 5

[Stefan Hristov]

Hi all,

many thanks for your answers! I wasn't expecting that many answers so fast. It's great to see such enthusiasm in the forum as i am quite new to Matlab.

I am going through all the solutions and trying to learn. :)

Best!

Stefan