How do I plot a datetime vs data within a cell array?

Hello! Say I have a nx2 cell array named CELL with the following data types per column:

column 1: datetime

column 2: double

Whenever I try to plot using plot(CELL{:,1},CELL{:,2}), the following error occur:

"Data inputs must match the axis configuration. A numeric axis must have numeric data inputs or data inputs which can be converted to double. "

NOTE: I also tried cell2mat(CELL{:,1}) to try if I can convert the datetime column into an array but the following error occurs:

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

May I ask how I can plot the datetime cell column against the double cell column? Thank you very much in advance.

[Rik]

You must either convert your data to single arrays, or use a loop. Note that {:} creates a comma separated list, so you should use normal parentheses in your call to cell2mat.

[Jonathan Macuroy]

I see. Thank you very much! :)

Answer 1

[Peter Perkins]

You almost certyainly do not want to store your data like that. For one thing, cell arrays are designed for complete generality, anything can be in any element, so you will find things that involve homogeneous data to be clumsy or unworkable (as you found). For another, the memory footprint will be much larger.

Use a table, or in this case a timetable. Not sure how you got where you are, but it's easy to convert. Say you have this cell array:

>> C
C =
  10×2 cell array
    {[01-Jul-2019]}    {[0.81472]}
    {[02-Jul-2019]}    {[0.90579]}
    {[03-Jul-2019]}    {[0.12699]}
    {[04-Jul-2019]}    {[0.91338]}
    {[05-Jul-2019]}    {[0.63236]}
    {[06-Jul-2019]}    {[0.09754]}
    {[07-Jul-2019]}    {[ 0.2785]}
    {[08-Jul-2019]}    {[0.54688]}
    {[09-Jul-2019]}    {[0.95751]}
    {[10-Jul-2019]}    {[0.96489]}
>> TT = table2timetable(cell2table(C,'VariableNames',{'Time','X'}))
TT =
  10×1 timetable
       Time           X   
    ___________    _______
    01-Jul-2019    0.81472
    02-Jul-2019    0.90579
    03-Jul-2019    0.12699
    04-Jul-2019    0.91338
    05-Jul-2019    0.63236
    06-Jul-2019    0.09754
    07-Jul-2019     0.2785
    08-Jul-2019    0.54688
    09-Jul-2019    0.95751
    10-Jul-2019    0.96489

At that point, plotting is simple.

    >> plot(TT.Time,TT.X)

But better still, create the timetable to begin with, instead of the cell array.

[Jonathan Macuroy]

Peter,

Hello! Yeah, I believe your suggestion to not use cell arrays when working with data is the right path. I instead created separate tables for them, with the datetime as a datetime array instead of a cell array. Thank you very much!