MATLAB: How to plot time on the x-axis if it is from 09pm to 09am (over midnight)

midnightplottime

Hi all,

i like to plot some data and the x-axis should be my timeline beginning from 09pm to 09am. When I tell MATLAB to plot my duration-variable (09pm to 09am in 5 sec steps), it shifts my plot so that the time beginns at midnight instead of 09pm.

Could somebody help me solving this problem and explain how to do it?

Thank you very much!

Best Answer

If you explicitly supply a date, this will not happen. The xtickformat function was introduced in R2016b, so you might not have it, but you can change the XTickLabel property directly.

alltime=linspace(...
    datetime(2018,2,24,21,0,0),...
    datetime(2018,2,25,09,0,0),...
    8640+1);
allHR=randi([50 100],8640,1);
figure(1),clf(1)
plot(alltime,allHR)
xtickformat('hh:mm:ss a')

Edit: changed time steps from 5 minutes to 5 seconds.

Related Solutions

MATLAB: Timezone to UTC: How to add duration vector to datetime vector

Frank, what's up is Daylight Saving Time, which occurred on March 8th this year. I'm guessing you knew that, but got mixed up in the time arithmetic. Here's what's going on. You have this:

>> time = ['2015/03/08 00:00';'2015/03/08 01:00';'2015/03/08 03:00';'2015/03/08 04:00'];
>> Time = datenum(time,'yyyy/mm/dd HH:MM')
Time =
                    736031
          736031.041666667
                736031.125
          736031.166666667

datenums don't know anything about time zones or DST. Those times mean whatever you want them to mean. Since you then do this ...

>> date = datetime(Time,'ConvertFrom','datenum','Timezone','America/Montreal')
date = 
   08-Mar-2015 00:00:00
   08-Mar-2015 01:00:00
   08-Mar-2015 03:00:00
   08-Mar-2015 04:00:00

... I assume you mean that those datenums are to be interpreted as times in the America/Montreal time zone. But what you've left out is this:

>> date.Format = [date.Format ' z']
date = 
   08-Mar-2015 00:00:00 UTC-5
   08-Mar-2015 01:00:00 UTC-5
   08-Mar-2015 03:00:00 UTC-4
   08-Mar-2015 04:00:00 UTC-4

The second and third times are only an hour apart. Then this ...

>> [UTC_Offset,dst] = tzoffset(date);
>> Date = date - UTC_Offset
Date = 
   08-Mar-2015 06:00:00 UTC-4
   08-Mar-2015 07:00:00 UTC-4
   08-Mar-2015 07:00:00 UTC-4
   08-Mar-2015 08:00:00 UTC-4

... adds 5 hours to the first and second times, but adds only 4 hours to the third and fourth times. But you're doing the addition in the America/Montreal time zone. Adding 5 hours to the first two puts them after the DST shift @2am, which makes them look like you added 6 hours. In other words, your array is not UTC, it's shifted America/Montreal. The easiest thing to do to get UTC times is this:

>> date.TimeZone = 'UTC'
date = 
   08-Mar-2015 05:00:00 UTC
   08-Mar-2015 06:00:00 UTC
   08-Mar-2015 07:00:00 UTC
   08-Mar-2015 08:00:00 UTC

Hope this helps.

MATLAB: Extract partial data from datetime using logics/vectorization

I would extract the time components first and then deal with grouping by day of the week. It's easy to keep this all organized in a table:

d = datetime(2021,1,1) + minutes(randi([0,10000],[100,1])); % cook up some data
d = sort(d);
t = table(d);
t.dow = weekday(d);
t.hour = hour(d);
t.min = minute(d);
% Get the hours for Tuesday (use {} to get results as an array, () as a table)
t{t.dow == 3, "hour"}

Best Answer

Related Solutions

MATLAB: Timezone to UTC: How to add duration vector to datetime vector

MATLAB: Extract partial data from datetime using logics/vectorization

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