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Hello,
I have excel file with three columns "Time", "Altitude, And "Shadow length" that I want to read in Matlab. I tried this commands below, however, the column "Time" format change to decimal number. What can I do to keep the time format the same?
Thank you!
T = readtable('Shadedata.xlsx');
opts = detectImportOptions('Shadedata.xlsx');
preview('Shadedata.xlsx',opts)

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Star Strider
Star Strider 2023 年 8 月 18 日
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One option is to use the datetime 'ConvertFrom' name-value pair. For the ‘value’ argument, both 'excel' and 'posixtime' work, with 'excel' appearing to be correct (in that it gives 15-minute intervals) —
% F = fileread('Shadedata.xlsx')
% C = readcell('Shadedata.xlsx')
T = readtable('Shadedata.xlsx', 'VAriableNamingRule','preserve')
T = 40×3 table
Time Altitude [degree celcius] Shadow length [m] _______ _________________________ _________________ 0.32292 1.34 2135.8 0.33333 2.34 808.83 0.34375 3.34 495.25 0.35417 4.34 357.42 0.36458 5.34 280.44 0.375 6.34 231.5 0.38542 7.34 197.77 0.39583 8.34 173.22 0.40625 17.92 154.65 0.41667 19.63 140.22 0.42708 21.22 128.79 0.4375 22.68 119.62 0.44792 24.02 112.22 0.45833 25.2 106.24 0.46875 26.24 101.45 0.47917 27.11 97.68
T1 = T;
T1.Time = datetime(T1.Time, 'ConvertFrom','excel')
T1 = 40×3 table
Time Altitude [degree celcius] Shadow length [m] ____________________ _________________________ _________________ 31-Dec-1899 07:45:00 1.34 2135.8 31-Dec-1899 08:00:00 2.34 808.83 31-Dec-1899 08:15:00 3.34 495.25 31-Dec-1899 08:30:00 4.34 357.42 31-Dec-1899 08:45:00 5.34 280.44 31-Dec-1899 09:00:00 6.34 231.5 31-Dec-1899 09:15:00 7.34 197.77 31-Dec-1899 09:30:00 8.34 173.22 31-Dec-1899 09:45:00 17.92 154.65 31-Dec-1899 10:00:00 19.63 140.22 31-Dec-1899 10:15:00 21.22 128.79 31-Dec-1899 10:30:00 22.68 119.62 31-Dec-1899 10:45:00 24.02 112.22 31-Dec-1899 11:00:00 25.2 106.24 31-Dec-1899 11:15:00 26.24 101.45 31-Dec-1899 11:30:00 27.11 97.68
T2 = T;
T2.Time = datetime(T2.Time, 'ConvertFrom','posixtime')
T2 = 40×3 table
Time Altitude [degree celcius] Shadow length [m] ____________________ _________________________ _________________ 01-Jan-1970 00:00:00 1.34 2135.8 01-Jan-1970 00:00:00 2.34 808.83 01-Jan-1970 00:00:00 3.34 495.25 01-Jan-1970 00:00:00 4.34 357.42 01-Jan-1970 00:00:00 5.34 280.44 01-Jan-1970 00:00:00 6.34 231.5 01-Jan-1970 00:00:00 7.34 197.77 01-Jan-1970 00:00:00 8.34 173.22 01-Jan-1970 00:00:00 17.92 154.65 01-Jan-1970 00:00:00 19.63 140.22 01-Jan-1970 00:00:00 21.22 128.79 01-Jan-1970 00:00:00 22.68 119.62 01-Jan-1970 00:00:00 24.02 112.22 01-Jan-1970 00:00:00 25.2 106.24 01-Jan-1970 00:00:00 26.24 101.45 01-Jan-1970 00:00:00 27.11 97.68
Choose the result that makes the best sense.
.

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Sanley Guerrier
Sanley Guerrier 2023 年 8 月 18 日
Looks great, Thank you!
my date is 10-Feb-2023, how do I update your code to have someting like 10-Feb-2023 07:45:00 ?
Les Beckham
Les Beckham 2023 年 8 月 18 日
Ran in:
Ran in:
One possible way to offset the data to that desired date is this:
T = readtable('Shadedata.xlsx', 'VariableNamingRule', 'preserve');
T1 = T;
offset = exceltime(datetime(2023, 2, 10));
T1.Time = T1.Time + offset;
T1.Time = datetime(T1.Time, 'ConvertFrom', 'excel')
T1 = 40×3 table
Time Altitude [degree celcius] Shadow length [m] ____________________ _________________________ _________________ 10-Feb-2023 07:45:00 1.34 2135.8 10-Feb-2023 08:00:00 2.34 808.83 10-Feb-2023 08:15:00 3.34 495.25 10-Feb-2023 08:30:00 4.34 357.42 10-Feb-2023 08:45:00 5.34 280.44 10-Feb-2023 09:00:00 6.34 231.5 10-Feb-2023 09:15:00 7.34 197.77 10-Feb-2023 09:30:00 8.34 173.22 10-Feb-2023 09:45:00 17.92 154.65 10-Feb-2023 10:00:00 19.63 140.22 10-Feb-2023 10:15:00 21.22 128.79 10-Feb-2023 10:30:00 22.68 119.62 10-Feb-2023 10:45:00 24.02 112.22 10-Feb-2023 11:00:00 25.2 106.24 10-Feb-2023 11:15:00 26.24 101.45 10-Feb-2023 11:30:00 27.11 97.68
Sanley Guerrier
Sanley Guerrier 2023 年 8 月 18 日
Perfect, thanks a lot!
Star Strider
Star Strider 2023 年 8 月 18 日
Ran in:
Ran in:
As always, my pleasure!
I don’t see anything that directly addresses that problem ('PivotYear' would only change the year) and dateshift doesn’t appear to provide the necessary options.
So, I improvised —
T = readtable('Shadedata.xlsx', 'VAriableNamingRule','preserve')
T = 40×3 table
Time Altitude [degree celcius] Shadow length [m] _______ _________________________ _________________ 0.32292 1.34 2135.8 0.33333 2.34 808.83 0.34375 3.34 495.25 0.35417 4.34 357.42 0.36458 5.34 280.44 0.375 6.34 231.5 0.38542 7.34 197.77 0.39583 8.34 173.22 0.40625 17.92 154.65 0.41667 19.63 140.22 0.42708 21.22 128.79 0.4375 22.68 119.62 0.44792 24.02 112.22 0.45833 25.2 106.24 0.46875 26.24 101.45 0.47917 27.11 97.68
T.Time = datetime(T.Time, 'ConvertFrom','excel')
T = 40×3 table
Time Altitude [degree celcius] Shadow length [m] ____________________ _________________________ _________________ 31-Dec-1899 07:45:00 1.34 2135.8 31-Dec-1899 08:00:00 2.34 808.83 31-Dec-1899 08:15:00 3.34 495.25 31-Dec-1899 08:30:00 4.34 357.42 31-Dec-1899 08:45:00 5.34 280.44 31-Dec-1899 09:00:00 6.34 231.5 31-Dec-1899 09:15:00 7.34 197.77 31-Dec-1899 09:30:00 8.34 173.22 31-Dec-1899 09:45:00 17.92 154.65 31-Dec-1899 10:00:00 19.63 140.22 31-Dec-1899 10:15:00 21.22 128.79 31-Dec-1899 10:30:00 22.68 119.62 31-Dec-1899 10:45:00 24.02 112.22 31-Dec-1899 11:00:00 25.2 106.24 31-Dec-1899 11:15:00 26.24 101.45 31-Dec-1899 11:30:00 27.11 97.68
[h,m,s] = hms(T.Time); % Get Time Data
T.Time = datetime([repmat([2023 2 10],numel(h),1) h m s]) % Create New Dates & Times
T = 40×3 table
Time Altitude [degree celcius] Shadow length [m] ____________________ _________________________ _________________ 10-Feb-2023 07:45:00 1.34 2135.8 10-Feb-2023 08:00:00 2.34 808.83 10-Feb-2023 08:15:00 3.34 495.25 10-Feb-2023 08:30:00 4.34 357.42 10-Feb-2023 08:45:00 5.34 280.44 10-Feb-2023 09:00:00 6.34 231.5 10-Feb-2023 09:15:00 7.34 197.77 10-Feb-2023 09:30:00 8.34 173.22 10-Feb-2023 09:45:00 17.92 154.65 10-Feb-2023 10:00:00 19.63 140.22 10-Feb-2023 10:15:00 21.22 128.79 10-Feb-2023 10:30:00 22.68 119.62 10-Feb-2023 10:45:00 24.02 112.22 10-Feb-2023 11:00:00 25.2 106.24 10-Feb-2023 11:15:00 26.24 101.45 10-Feb-2023 11:30:00 27.11 97.68
DI = cumsum([0; diff(hour(T.Time))<0]); % Check For Midnight Rollover
T.Time = T.Time + days(DI) % Increment Days For Midnight Rollovers
T = 40×3 table
Time Altitude [degree celcius] Shadow length [m] ____________________ _________________________ _________________ 10-Feb-2023 07:45:00 1.34 2135.8 10-Feb-2023 08:00:00 2.34 808.83 10-Feb-2023 08:15:00 3.34 495.25 10-Feb-2023 08:30:00 4.34 357.42 10-Feb-2023 08:45:00 5.34 280.44 10-Feb-2023 09:00:00 6.34 231.5 10-Feb-2023 09:15:00 7.34 197.77 10-Feb-2023 09:30:00 8.34 173.22 10-Feb-2023 09:45:00 17.92 154.65 10-Feb-2023 10:00:00 19.63 140.22 10-Feb-2023 10:15:00 21.22 128.79 10-Feb-2023 10:30:00 22.68 119.62 10-Feb-2023 10:45:00 24.02 112.22 10-Feb-2023 11:00:00 25.2 106.24 10-Feb-2023 11:15:00 26.24 101.45 10-Feb-2023 11:30:00 27.11 97.68
All the times are the same day here, however I included code that will increment the days in the event other data sets would have a midnight rollover. (I have used this approach with other problems.)
.
Sanley Guerrier
Sanley Guerrier 2023 年 8 月 18 日
Thanks a lot!
Star Strider
Star Strider 2023 年 8 月 18 日
As always, my pleasure!

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