Error using str2double on a cell array, getting NaN

I am trying to make a histogram of the frequency of safety violations, I am getting the data from an excel sheet that contains information like the location, time, and other descriptive information of the incidents. I pulled the time out to be able to plot but using the function I got NaN, the plot of course showed nothing.

ChillicotheInjury.RecordNo_=num2cell(ChillicotheInjury.RecordNo_)

a=class(ChillicotheInjury.Time)
b=str2double(ChillicotheInjury.Time(1))
c=ChillicotheInjury.Time(1)
d=class(i)
plot(1,i)

What could I do to fix this issue? I was told try using xlsread but when I did I got NaN and the date, it shows the day in dd/mm/yyyy format at the hour, column was all divided together.

a='cell' b=NaN c={'07:30:00'} d='double'

the rest of my code

SafetyDataOne=readtable('Incidents - Franklin Park Chillicothe Waynesville.xlsx');
SafetyDataTwo=readtable('Injuries - Franklin Park Chillicothe Waynesville.xlsx');
%Above lines import two excel sheets
SafetyDataTwo=SafetyDataTwo(:,[1:5]);
%Remove unnecceary columns
SafetyData=[SafetyDataOne;SafetyDataTwo];
%Combine into single table
d=SafetyData.Date;
%Date column is put into a varible 
d.Format='dd-MMM-yyyy';
Date = cellstr(d);
d.Format = 'hh:mm:ss';
Time = cellstr(d); 
%Break time column into more useful two columns
SafetyData=[SafetyData(:,1:2),Date,Time,SafetyData(:,4:5)];
% Put it together again
SafetyData.Properties.VariableNames([3 4])={'Date' 'Time'};
%Name the new columns
SafetyData=sortrows(SafetyData);
%Sort location column alphebetically 
Location=SafetyData.Location;

SafetyDataChillicothe=sortrows(SafetyData(1:248,:),5);
SafetyDataFranklinPark=sortrows(SafetyData(249:454,:),5);
SafetyDataWaynesville=sortrows(SafetyData(455:end,:),5);
%Sort alpabetically the type of injury experinced

CillicotheFirstAid=SafetyDataChillicothe(1:225,:);
ChillicotheMFAR=SafetyDataChillicothe(225:229,:);
ChillicotheOther=SafetyDataChillicothe(230:232,:);
ChillicotheProperty=SafetyDataChillicothe(233:243,:);
ChillicotheInjury=SafetyDataChillicothe(244:248,:);
%Create Variables of the different types of injuries/incidents

FranklinEnvironmental=SafetyDataFranklinPark(1:2,:);
FranklinFirstAid=SafetyDataFranklinPark(3:103,:);
FranklinMFAR=SafetyDataFranklinPark(104:109,:);
FranklinOther=SafetyDataFranklinPark(110:138,:);
FranklinProperty=SafetyDataFranklinPark(139:188,:);
FranklinInjury=SafetyDataFranklinPark(189:199,:);
FranklinVehicle=SafetyDataFranklinPark(199:206,:);
%Create Variables of the different types of injuries/incidents

WaynesvilleFirstAid=SafetyDataChillicothe(1:74,:);
WaynesvilleMFAR=SafetyDataChillicothe(75:80,:);
WaynesvilleOther=SafetyDataChillicothe(81:84,:);
WaynesvilleProperty=SafetyDataChillicothe(85:87,:);
WaynesvilleInjury=SafetyDataChillicothe(88:94,:);
%Create Variables of the different types of injuries/incidents

ChillicotheInjury.RecordNo_=num2cell(ChillicotheInjury.RecordNo_)

a=class(ChillicotheInjury.Time)
b=str2double(ChillicotheInjury.Time(1))
c=ChillicotheInjury.Time(1)
d=class(i)
plot(1,i)

%histogram(table2array(ChillicotheInjury(:,4)))

% data_numNEW  = table2array(ChillicotheInjury);
% data_numNEW = cellfun(@string,data_numNEW,'uni',0);
% data_numNEW = cellfun(@double,data_numNEW,'uni',0);
% data_numNEW = cell2mat(data_numNEW);
%ChillicotheInjury=class((ChillicotheInjury(:,4)))
%histogram(table2array(ChillicotheInjury(:,4)))

[the cyclist]

Can you upload all the data and code needed to replicate the problem? It's very difficult to debug issues like this without that.

[Alejandro Martinez]

I added a snippet of the doc i am working on, is that enough or do I add the actual excel sheet?

Answer 1

[Drishan Poovaya]

I understand you want to convert strings of date/time values into doubles so you can plot them. As per the image you attached, the format of the date/time is dd/mm/yyyy hh:mm.

As per the documentation of str2double , if str2double cannot convert text to a number, then it returns a NaN value which could be cause of the error you are facing

Rather than converting it to a double I would suggest you convert it into a datetime object, which makes it easy to get a plot of dates vs violations. Assuming you have all your date/time values stored in a cell array, the below code will convert them into a datetime array which can be used as the x axis vector for your plots

DtArray = datetime(ChillicotheInjury.Time, 'InputFormat', 'dd/MM/yyyy hh:mm'); 

DateTime doc :

https://www.mathworks.com/help/matlab/ref/datetime.html?s_tid=doc_ta#d123e285446