Accessing and synchronizing timetables in cell array?

I've been working on a script to examine salinity around specific time ranges around high tide (e.g. +/- 30 min, 1 hour, 2 hours, etc), and I'm trying to keep it as systematic as possible so that I can import different dates/locations and run it without any changes. Right now I'm at the point where I have a 296x1 cell array (mr2), with a 5x1 timetable in each cell. Essentially, I'm trying to extract the timetables from this cell array to create one combined timetable. Each timetable has the same variable, and the timestamps are chronological going through cells 1:296. I've been attempting this through a for loop, although I think I'm having an issue with the indexing.

%% Convert cell array to timetable

lengthmr = length(mr2).*5;
iterations = zeros(lengthmr,1);
sz = [lengthmr 2];
varTypes = ["datetime","double"];
varNames = ["Timestamp","Sal_psu"];

T = table('Size',sz,'VariableTypes',varTypes,'VariableNames',varNames);

for i = 1:length(iterations)
    T(i,"Sal_psu") = mr2{i,1}(i,1);
end

The error message I receive is:

Error using ()

Row index exceeds table dimensions.

Error in COMPARE_salinity_model_MRB_v2m (line 46)

T(i,"Sal_psu") = mr2{i,1}(i,1);

So I know the indexing I'm doing is quite off, but I've been trying to troubleshoot for a few days now and thought I'd reach out to the community. I will also attach the variables to run this bit of code.

TIA!

[Mikaela Martiros]

Also, apologies if this is a bit clunky! I tend to write scripts by working through my logic step by step, so I often have a lot of variables or a lot of steps for fairly simple processes. I usually work these out after getting what I need from the code, but yeah, be gentle!

Answer 1

[Stephen23]

Do not use a loop for this! The simple MATLAB approach is to use a comma-separated list:

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

https://www.mathworks.com/matlabcentral/answers/1656435-tutorial-comma-separated-lists-and-how-to-use-them

For example:

S = load('salinity_code_troubleshoot.mat');
mr2 = S.mr2

mr2 = 296×1 cell array
    {5×1 timetable}
    {5×1 timetable}
    {5×1 timetable}
    {5×1 timetable}
    {5×1 timetable}
    {5×1 timetable}
    {5×1 timetable}
    {5×1 timetable}
    {5×1 timetable}
    {5×1 timetable}
    {5×1 timetable}
    {5×1 timetable}
    {5×1 timetable}
    {5×1 timetable}
    {5×1 timetable}
    {5×1 timetable}

T = vertcat(mr2{:}) % comma-separated list

T = 1480×1 timetable
         Timestamp         Sal_psu
    ___________________    _______

    2022-05-12 19:30:00      6.25 
    2022-05-12 19:45:00      7.09 
    2022-05-12 20:00:00      7.78 
    2022-05-12 20:15:00       8.2 
    2022-05-12 20:30:00      8.37 
    2022-05-13 08:00:00      6.54 
    2022-05-13 08:15:00      7.13 
    2022-05-13 08:30:00      7.82 
    2022-05-13 08:45:00      8.04 
    2022-05-13 09:00:00       8.1 
    2022-05-13 20:30:00      8.63 
    2022-05-13 20:45:00      9.38 
    2022-05-13 21:00:00      9.82 
    2022-05-13 21:15:00     10.08 
    2022-05-13 21:30:00     10.22 
    2022-05-14 08:45:00      6.32 

[Luca Ferro]

way better solution than mine, thank you!

[Mikaela Martiros]

Beautiful! Always learning, thank you for the solution and documentation links!

Answer 2

[Luca Ferro]

[cMax,~]=size(mr2);

C=mr2{1} %needs the first 5 elements of the table as preallocation

for ii=1:cMax

C=[C ; mr2{ii}]; %vertically concatenate tables

end

C=sortrows(C); %the data in mr2 is not sorted timewise, so if you want it sorted add this line

Hopefully this is what you were looking for.

[Mikaela Martiros]

Thank you for your response!