Error when trying to remove rows with specific values from cell array.

I have a cell array that looks like this with strings and numbers

I'm trying to write simple code that will remove entire rows in the array if numbers 1-20 are present in column 1:

toremove = [1:20];
event_time(ismember(event_time(:,1),toremove)) = [];

However I receive this error when I run my code

Error using cell/ismember
Input A of class cell and input B of class double must be cell arrays of character vectors, unless one is a character vector.

How would I index event_time by the numbers in column 1? They are not strings/characters so strcmp does not work, and treating them as integers, as above does not work either. Many thanks!

Answer 1

[Star Strider]

Try this:

CA = num2cell(randi(50, 25, 5));                            % Create Cell Array
idx = cellfun(@(x)ismember(x, 1:20), CA(:,1));              % Logical Vector Selecting (1:20) In Column #1
CAedited = CA(~idx,:);                                      % Eliminat Rows Meeting Criteria

Use your own cell array for ‘CA’.

[Aleya Marzuki]

Hi, thank you. The idx part worked when I set 'Uniform Output' to false as so:

idx = cellfun(@(x)ismember(x, 1:20), event_time(:,1), 'UniformOutput', false); 

As the first row begins with 'Trial'. But when I tried to use the index to remove certain rows I received the following error:

Undefined unary operator '~' for input arguments of type 'cell'.

I suppose the issue stems from me having both strings and numbers in the array?

[Star Strider]

My code should work with your cell array. It worked with the cell array I created to test my code.

I do not have your cell array (or a representative sample of it) to work with. It would be easier to solve this problem if I did.

[Aleya Marzuki]

Yes I tried it on your cell array and indeed it worked fine. I've attached my cell array to the question, let me know if you're able to access it, thank you!

[Star Strider]

There was a minor problem with respect to the class of the ‘idx’ vector that was not a problem with my cell array I used to test my code.

This appears to solve that problem:

C1 = load('blk1_event_times.mat');                                      % Read  .mat  File
event_time = C1.event_time;                                             % Cell Array
idx = cellfun(@(x)ismember(x, 1:20), event_time(2:end,1), 'Uni',0);     % Logical Vector Selecting (1:20) In Column #1
event_time_edited = event_time(~[idx{:}],:);                            % Eliminate Rows Meeting Criteria

The ‘idx’ logical vector cell array needs to be converted to a ‘regular’ (for lack of a better adjective) logical vector for this to work. One approach would be to use the cell2mat function, although the ‘shorthand’ ‘[idx{:}]’ works well here.

I did not look closely at the output ‘event_time_edited’, however the original cell array is (314x8) and ‘event_time_edited’ is (273x8), so I assume it works correctly.

[Aleya Marzuki]

Many thanks! I tweaked your code a bit so that idx takes into account the first row in event_time which contains 'trial'. Without taking this into account, the idx file is too short (with one row less than the number of rows of the original file)

idx = cellfun(@(x)ismember(x, 1:20), event_time(1:end,1), 'Uni',0); % Idx outputs 1 if 1-20 is in Column #1 and 0 otherwise
idx(1,:)=  {[0]}; % need to convert first row of index to 0 because the string 'trial' shows [0,0,0,0,0], which will make the index fail to work
event_time = event_time(~[idx{:}],:); % remove any rows where idx = 1  

[Star Strider]

As always, my pleasure!