Reading excel data from file and using datetick

Below is a screenshot of an excel file I have and I am trying to plot the first column as x-axis and second column as y-axis.

So, I wrote the following code

    function letsplot

        exl = actxserver('excel.application');
        exlWkbk = exl.Workbooks;
        folder = 'C:\Users\shankyaw\Desktop\icandoit';
        FilesNeeded = dir(fullfile(folder,'\*.xlsx'))
        sd = length(FilesNeeded)
        lBoxList = cell(sd,1);
        myRange1 = 'A1:A36000';
        myRange2 = 'B1:B36000';
        for i = 1:sd
            exlFile = exlWkbk.Open(fullfile(folder,FilesNeeded(i).name));
            exlSheet1=exlFile.Sheets.Item('sheet1');
            if i == 1
            time_myar = exlSheet1.Range(myRange1).Value; %%problem is here??
            Efield(:,i) = cell2mat(exlSheet1.Range(myRange2).Value);
            else
            Efield(:,i) = cell2mat(exlSheet1.Range(myRange2).Value);    
            end
            lBoxList{i,1} = FilesNeeded(i).name;
        end

        timetime = datenum(time_myar);  %%problem is here??
        stem(timetime,Efield(:,x));
        datetick('x','keeplimits','keepticks');
        exlWkbk.Close
        exl.Quit
    end

However, I get the error message that says

Error using datenum (line 179) DATENUM failed.

Error in EFieldPlotting (line 10) timetime = datenum(time_myar);

Caused by: Error using datevec (line 104) The input to DATEVEC was not an array of strings.

I tried both cellstr and datestr as below:

time_myar = cellstr(exlSheet1.Range(myRange1).Value); time_myar = datestr(exlSheet1.Range(myRange1).Value);

But, the error is still there. Can some kind soul help me guide how to overcome this error message.

Thanks.

Answer 1

[dpb]

Dates were read as numeric Excel dates; not as string values. See exceltime to convert to Matlab-consistent date numbers if have late revision otherwise, read the notes on the differences between Excel and Matlab and make the fixup manually.

NB: though, unless you have more resolution than displayed in the spreadsheet (always a possibility, but not a given), there isn't enough precision to make the values unique for a major portion of the data shown.