getting first element of each cell array with different sizes

Hi,

I have a 205 x 1 cell with diffferent sizes and I want to extract only the first element of each cell. For example, I have:

[8,14]

[10,14,15]

[9,14]

[5,14] etc till 205

and the result should be:

8

10

9

5.

Thanks a lot!

M.

Answer 1

[Stephen23]

>> C = {[8,14];[10,14,15];[9,14];[5,14]};
>> cellfun(@(v)v(1),C)
ans =
    8
   10
    9
    5

[Stephen23]

And to allow for empty arrays:

>> C = {[8,14];[10,14,15];[9,14];[5,14];[]};
>> idx = ~cellfun('isempty',C);
>> out = zeros(size(C));
>> out(idx) = cellfun(@(v)v(1),C(idx))
out =
    8
   10
    9
    5
    0

Answer 2

[Christian Keine]

There are at least two possible ways this could be done. First, you could loop through the cell array and extract the first value of each cell. This is, however, probably not the most elegant or fastest solution. The second option is to use cellfun in combination with an anonymous function which extracts only the first value of each cell, which should work faster for large arrays and is easier to read.

To do so, first define the function that should be executed for each cell:

fun = @(x) x(1)

Then apply this function to each cell in the array using cellfun with x being you cell array

firstElement = cellfun(fun,x)

Using your data it would look like this:

x = {[8,14],[10,14,15],[9,14],[5,14]}
fun = @(x) x(1)
firstElement = cellfun(fun,x)

Hope this is helpful.

[sensation]

Hi, thanks both for the kind answers. It works fine as you suggested on small example, but when I try to run it on my whole 205 X 1 cell I get an error: Index exceeds matrix dimensions.

Error in @(x)x(1)

Any clue whys this happen?

Thanks a lot!

[sensation]

Just saw that I have in my data instead of number I have nan someties like:

[8,14]

[10,14,15]

[]

[9,14].

Do you know how to include also this in a way to put zero in an output if there is nothing in a cell like?

8

10

0

9

Thanks!

[Stephen23]

@sensation: see my comment, which shows exactly how to do this.

Answer 3

[Daniel Rieger]

Hello guys,

what if i only want to obtain the first entry of the first cell?

Or more general: what if i want a specific entry not for each but only for one cell?

I could also use and then cut out the entries that i dont need, but is there a more elegant way?

% N: wanted entry
all_entry = cellfun(@(v)v(1),C) 
wanted_entry = all_entry(N)

[Stephen23]

C{N}(1)

https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html