Convert cell array
Convert cell arrays element-wise (cellfun)
Apply a function to each cell element
X = cellfun(@function , CellArray)
Convert cell array into matrix
% convert numbers from text string cell-array 'C' into a numerical matrix 'X'
C = {'11','12','13','14','15';...
'21','22','23','24','25'}
X = cellfun(@str2num, C )
11 12 13 14 15
21 22 23 24 25
% convert subset of cell-array into matrix
X = cellfun(@str2num, C(2 , 1:3) ) % elements 1...3 of second row
21 22 23
X = cellfun(@str2num, C(: , 3) ) % convert 3rd column
13
23
Multiple inputs and custom functions
X = cellfun(@(x) myfunction(x,y) , CellArray)
Example - Customized function
% define custom function
function c = myfunction(s,th)
% convert string into numerical value and check if larger than threshold 'th'
x = str2num(s);
if isempty(x), x=NaN; end
c = x > th;
% apply custom function to each cell array (check if text numbers are larger than 12)
C = {'11','12','13','14','15';...
'21','22','23','24','25'}
X = cellfun(@(x) myfunction(x,12) , C )
0 0 1 1 1
1 1 1 1 1
One-liner: small custom functions inside cellfunc
% same x>12 check as before, but as short version inside the cellfun
% find all text-numbers larger than 12 (convert string into numerical values and compare)
C = {'11','12','13','14','15';...
'21','22','23','24','25'}
X = cellfun(@(x) str2num(x)>12 , C )
0 0 1 1 1
1 1 1 1 1
% convert string into numbers and divide by 100
X = cellfun(@(x) str2num(x)/100 , C )
0.1100 0.1200 0.1300 0.1400 0.1500
0.2100 0.2200 0.2300 0.2400 0.2500
% add prefix
X = cellfun(@(x) {['T_',x]}, C )
{'T_11'} {'T_12'} {'T_13'} {'T_14'} {'T_15'}
{'T_21'} {'T_22'} {'T_23'} {'T_24'} {'T_25'}
% replace space with underscore for all elements in cell
C = {'A 1','A 2','A 3'};
X = cellfun(@(x) {strrep(x,' ','_')} , C)
{'A_1'} {'A_2'} {'A_3'}
Filter (select) text of cell elements
Get cell elements containing specific text (keywords or substring)
% get index location of 'Control' samples
C = {'A1','A2','A3','','B1','B2','B3','','Control','Control','Control'};
id = find( cellfun(@(x) isequal(x,'Control'), C) )
9 10 11
% get location of all cell elements that contain substring 'B' (find cells whose output of strfind is not ('~') empty)
id = find( cellfun(@(x) ~isempty(strfind(x,'B')), C) )
5 6 7
C(id)
{'B1'} {'B2'} {'B3'}
% get index of cells that starts with 'CTR' (control) at the first 3 letters
C={'CTR_2','TIME_1','TIME_2','TIME_3','CTR_2','TIME_4','TIME_5'}
idx = cellfun(@(x) isequal('CTR',x(1:3)), C )
1 0 0 0 1 0 0
find(idx)
1 5
Replace all text elements 'Control' with 'CTR'
% get index location of 'Control' samples and overwrite with 'CTR'
C = {'A1','A2','A3','','B1','B2','B3','','Control','Control','Control'};
C( find(cellfun(@(x) isequal(x,'Control'), C)) ) = {'CTR'}
see also: → How to assign a single value to multiple cells
Find and remove empty cell elements
C = {'A1','A2','A3','','B1','B2','B3','','Control','Control','Control'};
% find all empty elements in cell array
idx = cellfun(@isempty, C)
0 0 0 1 0 0 0 1 0 0 0
find(idx)
4 8
% get subset containing all elements that are not ('~') empty
X = C( ~cellfun(@isempty, C) )
{'A1'} {'A2'} {'A3'} {'B1'} {'B2'} {'B3'} {'Control'} {'Control'} {'Control'}