Multiple table input issues

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Pesach Nestlebaum
Pesach Nestlebaum on 4 May 2022
Commented: Voss on 5 May 2022
I have a script that reads multiple tables that contain columns such as "Light", "Temp", "Weight". Each row in these tables represents a "trigger", where the light level, temperature and weight are all recorded.
The script finds which hour contains the greatest number of "triggers" and assigns it to a variable. If you run the script, the variable "intlist" represents the hours with the greatest number of triggers for each table passed through the script.
My issue is, I would like to perform a further action and create an array for the interval where there is the most triggers in each table. I can accomplish this once, for the latest table that the script runs, but I cannot for the life of me get it to work for all the tables. The output I need would be 4 arrays, each listing the lightlevels corresponding the the rows within the interval of highest trigger number.
I believe there is something wrong with the way I structured this loop but I cannot figure out where it is going wrong.
I will attach the script and all 4 tables.
[file_list,path_n] = uigetfile('.xlsx','MultiSelect','on');
if iscell(file_list)==0
file_list=(file_list);
end
for i=1:length(file_list)
filename=file_list{i};
T1 = readtable([path_n filename]);
lidx = T1.Light<=4;
T1.Light(lidx) = (NaN);
Tt = [repmat(fix(now), size(T1,1), 1) + T1.Time];
T1.Time = datetime(Tt, 'ConvertFrom','datenum');
T1.Trigger = ones(size(T1.Time));
TT1 = table2timetable(T1);
TT1c = retime(TT1,'hourly','count');
[maxEvent,idx] = max(TT1c.Trigger);
intlist(i)=idx;
hourlist=hour(T1.Time)==idx;
lightlevels=T1.Light(hourlist);
end

Accepted Answer

Voss
Voss on 5 May 2022
Since lightlevels is a vector, and that vector might be different lengths for different files, it makes sense to store those vectors in a cell array and set one element of that cell array each time through the for loop.
[file_list,path_n] = uigetfile('.xlsx','MultiSelect','on');
if ~iscell(file_list)
file_list = {file_list}; % use { } here, by the way
end
n_files = numel(file_list);
lightlevels = cell(1,n_files); % lightlevels is a cell array now
intlist = zeros(1,n_files); % and intlist is a numeric array (in case you need it)
for i = 1:n_files
T1 = readtable([path_n file_list{i}]);
lidx = T1.Light<=4;
T1.Light(lidx) = NaN;
Tt = repmat(fix(now), size(T1,1), 1) + T1.Time;
T1.Time = datetime(Tt, 'ConvertFrom','datenum');
T1.Trigger = ones(size(T1.Time));
TT1 = table2timetable(T1);
TT1c = retime(TT1,'hourly','count');
[maxEvent,idx] = max(TT1c.Trigger);
intlist(i)=idx; % set the i-th element of intlist
hourlist = hour(T1.Time)==idx;
lightlevels{i} = T1.Light(hourlist); % set the i-th element of lightlevels
end
disp(lightlevels);
{13×1 double} {15×1 double} {12×1 double} {23×1 double}
lightlevels{1}
ans = 13×1
9 10 10 10 10 10 10 10 10 10
lightlevels{2}
ans = 15×1
10 10 10 10 10 10 10 10 10 10

More Answers (1)

Geoff Hayes
Geoff Hayes on 5 May 2022
@Peder Axensten - try creating a cell array of the data that you wish to save (I'm assuming that each iteration could produce a different number of lightlevels. For example,
lightlevels = {};
for i=1:length(file_list)
% code from above
hourlist=hour(T1.Time)==idx;
lightlevels{i} = T1.Light(hourlist);
end
  1 Comment
Pesach Nestlebaum
Pesach Nestlebaum on 5 May 2022
Ok, it created a 1 x 4 cell, but only the 4th column is occupied with a lightlevel list. Column 1 - 3 are empty.

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