How to label the points on x axis in hours.

Hi

I have a satellite timetsamp data in the form of '2016-02-05T01:01:24Z' I have used the matlab codes to remove T, Z and time in hours. I want to plot several days data according to time in hours with interval of 2 hrs. When I'm using the simple plot application, the axis is showing the time in days. Im intresetd to get the x axis in hours since the data also have Time in hours. How can I do this. My codes are

% Remove T and Z and time in HH:mm:ss from timestamp

TM1 = strrep(Timestamp, 'T', ' ');

TM2 = strrep(TM1, 'Z', ' ');

TmF = datetime(TM2, 'InputFormat','yyyy-MM-dd HH:mm:ss', 'Format','HH:mm:ss');

% Plot graph

plot(TmF,VTEC)

Im also attaching the simple plot which shows x axis in days.

Answer 1

[Star Strider]

Use this approach to convert the strings to datetime arrays:

old = {'2020-08-03T20:40:00.111Z'; '2020-08-03T21:40:01.123Z'};
time = datetime(old, 'InputFormat','yyyy-MM-dd''T''HH:mm:ss.SSS''Z''', 'TimeZone','UTC', 'Format','yyyy-MMM-dd HH:mm:ss.SSS')

time = 2×1 datetime array
   2020-Aug-03 20:40:00.111
   2020-Aug-03 21:40:01.123

time_in_hours = hour(time)

time_in_hours = 2×1

20 21

Then, plot the data against ‘time_in_hours’.

.

[Vikash Raj]

The time that I obtained using the above codes rounds the time to whole values example 20:40:00.111 to 20.I need the time as it is. How can I do that.

[Star Strider]

O.K. I misunderstood.

See Plot Dates and Durations, Format for Date Tick Labels, and xtickformat.

Answer 2

[Cris LaPierre]

First, you don't have to remove the T and Z. Just use the proper InputFormat for your timestamp

t='2016-02-05T01:01:24Z';
T = datetime(t,'InputFormat','yyyy-MM-dd''T''HH:mm:ss''Z')

T = datetime
   05-Feb-2016 01:01:24

Once you have your times, just plot the data with datetimes on X. Then use xtickformat to set the display format to hours.

plot(T,5,'x')
xtickformat('HH')

If you don't want the date at all, consider using the timeofday function.

figure
plot(timeofday(T),5,'x')
xtickformat('h')

Answer 3

[Vikash Raj]

Hi Thank you for the codes. This codes are not working in R2021 matlab program. When I run this codes it is giving error.

[Cris LaPierre]

It may not be working with your code, but it certainly works in R2021b. If you look at the top of my answer on the right, you will see it says 'Ran in: R2021b'.

[Vikash Raj]

Thanks. Perviously I ran those codes in 2015 it was working well. Recently I was able to install 2021 but this time it is giving some errors. I will try to see what is wrong. Thanks for your help.

[Cris LaPierre]

Share your error messages. Copy and share all the red text.

[Vikash Raj]

Hi Im getting this error.

Error using datetime (line 668)

Input data must be a numeric array, a string array, a cell array containing character vectors, or a char matrix.

When I imported the time data using the numeric matrix the data's were replaced by NaN. So importing the data using column Vectors and Cell Array reads the data in the matlab command however the maybe the codes are not working with this arrays.

[Cris LaPierre]

Please attach your data file to your post using the paperclip icon.

[Vikash Raj]

Hi

Please find the sample data attached.