Convert cell to duration array

Hi,

I had a program that was using time stored as seconds (double), I'm converting it to "duration" datatype, so the plots look nicer, natively displayed as HH:MM:SS.

However, I need to extract duration data stored in portions of a cell array to make a duration array.

%Simplified example with time as double:
TimingCell = {0; 63; 122} %doubles in a cell (0min, 1min03, 2min02)
MyArray = cell2mat(TimingCell)    % Works : array of doubles

Now that I have converted to duration:

%Simplified example with time as duration:
TimingCell = {duration(0,0,0); duration(0,1,3); duration(0,2,2)} %durations in a cell (0min, 1min03, 2min02)
MyArray = cell2mat(TimingCell)    % Does not work (wanted result: array of durations)

I get:

Error using cell2mat (line 52)

CELL2MAT does not support cell arrays containing cell arrays or objects.

I would like to get a duration array, I want something like the array created by this line:

MyArray = duration([0;0;0], [0;1;2], [0;3;1])

To summarize my question:

Is there an elegant equivalent to "cell2mat" when cell content is "duration"?

Thanks in advance for your time,

Corentin

Answer 1

[Stephen23]

"Is there an elegant equivalent to "cell2mat" when cell content is "duration"?"

Yes, this is really easy with a comma-separated list and concatenation, which does much the same thing as cell2mat, possibly with reshape if required.

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

>> TimingCell = {duration(0,0,0); duration(0,1,3); duration(0,2,2)}
TimingCell = 
    [00:00:00]
    [00:01:03]
    [00:02:02]
>> MyArray = vertcat(TimingCell{:})
MyArray = 
   00:00:00
   00:01:03
   00:02:02

[Corentin OGER]

Great, thanks Stephen!

It works just like cell2mat for my case!

Answer 2

[convert_to_metric]

Hi Corentin,

Since all of your data can be stored as either an array of doubles or an array of durations, you can probably skip using cell arrays altoghether. This would turn your second example into a one liner by converting the curly brackets into square brackets:

TimingCell = [duration(0,0,0); duration(0,1,3); duration(0,2,2)] %durations in aan array (0min, 1min03, 2min02)

Or if your original timing data is already stored as a cell array with each cell containg a double representing seconds: convert that cell array to a matrix using cell2mat, before making use of the duration function with the help of the seconds function. The example below uses the format property to have the output look the way you want it. Note that the output of the seconds function is already a duration, which may be sufficient for your needs.

TimingCell = {0; 63; 122} %doubles in a cell (0min, 1min03, 2min02)
MyArray = cell2mat(TimingCell)    % Works : array of doubles
MyArray2 = duration(seconds(MyArray),'format','hh:mm:ss')

[Corentin OGER]

Hi c2m, and thank you for your reply,

In fact, only a part of my cell contains duration data, the rest contains strings, laid out like this:

TimingCell =
  5×3 cell array
    [00:00:00]    [00:00:02]    'Starting Phase' 
    [00:00:05]    [00:00:20]    'Acceleration'   
    [00:00:20]    [00:02:30]    'Sustained speed'
    [00:02:30]    [00:02:45]    'Braking'        
    [00:02:45]    [00:02:47]    'Stopping'     

(this derives from a GUI table which the user can edit manually)

In the original version of my program, the first two colums were doubles, I used it as a database containing all timing information. I used cell2mat to retrieve only one column with cell2mat. Since I cannot retrieve a whole column at once, I'm probably going to use one table only with duration datatype, and keep a cell only for text descriptions.

[Corentin OGER]

In the end I converted to using a "table" to store my data, it's more ceonvenient than a cell for my use (it means that I have to rewrite a lot of code since several function access ths data but it looks cleaner)

DonneesTimings = 
     Start        Stop         Description   
    ________    ________    _________________
    00:00:00    00:00:02    'Starting Phase' 
    00:00:05    00:00:20    'Acceleration'   
    00:00:20    00:02:30    'Sustained speed'
    00:02:30    00:02:45    'Braking'        
    00:02:45    00:02:47    'Stopping'     

Answer 3

[Corentin OGER]

In case someone faces the same issue, I'll update what I really did in the end.

I used the "table" type of structure, which accepts mixed datatypes (like cells) but is easier to access directly. Each column is like a field in a struct, the difference being that they must all have the same number of rows. It's convenient to delete a complete row at once.

DonneesTimings = 

     Start        Stop         Description   
    ________    ________    _________________

    00:00:00    00:00:02    'Starting Phase' 
    00:00:05    00:00:20    'Acceleration'   
    00:00:20    00:02:30    'Sustained speed'
    00:02:30    00:02:45    'Braking'        
    00:02:45    00:02:47    'Stopping'