Extract time (hour+minute+second) from datetime vector

148 次查看（过去 30 天）
Ariana
Ariana 2023-10-25
移动：Dyuman Joshi 2023-10-25
I have an array that has datetime in one column, and a rate in the second column. i want to make a plot that just has on the x axis, a 24 hour day, and I want to see how the data varies over the course of the day. My dataset is a month long - so I'd like to plot all of that data and visualize it by time of day.
i don't know how to extract just the hour+minute+second data in ONE column. I know I can get hour separately, minute separately, etc. but I just want a column that says 01:30:22 for example, for each datetime value I have. I've looked at the function datetime but I'm pretty sure that gives me day as well? I JUST want time in the output
For reference, my table (BNFrates) has datetime in this format: 738771.683333333
Thank you!

请先登录，再回答此问题。

采纳的回答

Ariana
Ariana 2023-10-25
hi everyone,thank you to everyone who answered! I figured it out, and this is the code I used:
If datetimeBNF is the column with the original datetimes:
formattedDatetimes = cell(size(datetimeBNF));
for i = 1:numel(datetimeBNF)
formattedDatetimes{i} = datestr(datetimeBNF(i), 'HH:MM:SS');
end

更多回答（2 个）

Steven Lord
Steven Lord 2023-10-25
Ran in:
If you can use a datetime array instead of serial date numbers (or convert the serial date numbers to datetime):
rightnow = datetime('now')
rightnow = datetime
25-Oct-2023 18:07:00
use the timeofday function.
[timeSinceMidnight, midnight] = timeofday(rightnow)
timeSinceMidnight = duration
18:07:00
midnight = datetime
25-Oct-2023
To convert, first let's get the serial date number (you wouldn't need to do this, as you already have it. I need to do it so I can show you the results.)
format longg
serialDateNumber = datenum(rightnow)
serialDateNumber =
739184.754871983
Then call datetime with an option:
rightnow2 = datetime(serialDateNumber, 'ConvertFrom', 'datenum')
rightnow2 = datetime
25-Oct-2023 18:07:00
Dyuman Joshi
Dyuman Joshi 2023-10-25
移动：Dyuman Joshi 2023-10-25
Ran in:
Here's an approach -
in = load('example_array.mat')
in = struct with fields:
BNFratesall_NaN1: [21×2 double]
vec = in.BNFratesall_NaN1;
%Convert the dates to datetime()
dt = datetime(vec(:,1), 'ConvertFrom', 'datenum')
dt = 21×1 datetime array
07-Sep-2022 16:22:00 07-Sep-2022 16:23:59 07-Sep-2022 16:25:59 07-Sep-2022 16:27:59 07-Sep-2022 16:30:00 07-Sep-2022 16:32:00 07-Sep-2022 16:34:00 07-Sep-2022 16:36:00 07-Sep-2022 16:38:00 07-Sep-2022 16:40:00 07-Sep-2022 16:41:59 07-Sep-2022 16:43:59 07-Sep-2022 16:45:59 07-Sep-2022 16:48:00 07-Sep-2022 16:50:00 07-Sep-2022 16:52:00 07-Sep-2022 16:54:00 07-Sep-2022 16:56:00 07-Sep-2022 16:57:59 07-Sep-2022 16:59:59 07-Sep-2022 17:01:59
%Get the hour, minute and second values
[h,m,s] = hms(dt);
%Get the output as a duration() array
out = duration(h,m,s)
out = 21×1 duration array
16:22:00 16:23:59 16:25:59 16:27:59 16:30:00 16:32:00 16:34:00 16:36:00 16:38:00 16:40:00 16:41:59 16:43:59 16:45:59 16:48:00 16:50:00 16:52:00 16:54:00 16:56:00 16:57:59 16:59:59 17:01:59

类别

在 Help Center 和 File Exchange 中查找有关 Dates and Time 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by