How I can plot time on x axis with a interval of 2hrs from 0 to 24hrs

Hi.

I have a 10600 timestamp data in the form of 2015 - 01 -19T12:55:18Z which I need to plot aginst vertical total electron content. How can I remove T and Z and howI can plot time on x axis with a interval of 2hrs from 0 to 24hrs against vertical total electron content. Im very new to matlab software and Im doing a masters program to do my data analysis. Any help and suggestion will be highly appriciated.

Answer 1

[Walter Roberson]

TS = {'2015 - 01 -19T12:55:18Z', '2015 - 01 -19T23:17:29Z', }

TS = 1×2 cell array
    {'2015 - 01 -19T12:55:18Z'}    {'2015 - 01 -19T23:17:29Z'}

t = datetime(TS, 'inputformat', "yyyy - MM -dd'T'HH:mm:ss'Z'", 'TimeZone', 'GMT')

t = 1×2 datetime array
   19-Jan-2015 12:55:18   19-Jan-2015 23:17:29

plot(t, [1 2])

[Vikash Raj]

Thank you for your suggestion Walter Roberson however Im getting a Error: stating Unexpected MATLAB expression when is run this codes:

t = datetime(TS, 'inputformat', "yyyy - MM -dd'T'HH:mm:ss'Z'", 'TimeZone', 'GMT')

[Walter Roberson]

Are you using R2016b or earlier?

[Vikash Raj]

Im using R2015a

[Walter Roberson]

t = datetime(TS, 'inputformat', 'yyyy - MM -dd''T''HH:mm:ss''Z''', 'TimeZone', 'GMT')

[Walter Roberson]

You might need

plot(datenum(t), y)
datetick('x', 'HH')

[Vikash Raj]

Thank you. I have used the codes its working well. When I have plotted the graph on the time axis its all reading zero. How can a lable this x axis withtime interval of 2 hours starting from 0 to 24 hrs

[Walter Roberson]

t = datetime('now') + sort(minutes(randi([0 24*60], 1, 30)))

t = 1×30 datetime array
   30-Sep-2021 21:49:07   30-Sep-2021 22:15:07   30-Sep-2021 22:38:07   30-Sep-2021 23:02:07   30-Sep-2021 23:09:07   01-Oct-2021 00:45:07   01-Oct-2021 01:18:07   01-Oct-2021 02:52:07   01-Oct-2021 04:23:07   01-Oct-2021 05:35:07   01-Oct-2021 06:04:07   01-Oct-2021 06:30:07   01-Oct-2021 08:25:07   01-Oct-2021 08:34:07   01-Oct-2021 08:49:07   01-Oct-2021 09:28:07   01-Oct-2021 10:17:07   01-Oct-2021 10:42:07   01-Oct-2021 11:31:07   01-Oct-2021 11:44:07   01-Oct-2021 12:03:07   01-Oct-2021 14:27:07   01-Oct-2021 14:52:07   01-Oct-2021 15:42:07   01-Oct-2021 16:37:07   01-Oct-2021 17:48:07   01-Oct-2021 18:57:07   01-Oct-2021 19:48:07   01-Oct-2021 20:32:07   01-Oct-2021 21:12:07

y = rand(size(t))

y = 1×30

0.5071 0.2970 0.6975 0.0170 0.4546 0.5702 0.4778 0.8475 0.2032 0.9529 0.2908 0.2385 0.7161 0.6557 0.0726 0.3264 0.2269 0.2628 0.1820 0.3982 0.3167 0.2207 0.9381 0.6914 0.6869 0.5304 0.3496 0.8455 0.5153 0.9506

plot(datenum(t), y)
datetick('x', 'HH')

Is it possible that what you tried was more like

x = 0:2:24

x = 1×13

0 2 4 6 8 10 12 14 16 18 20 22 24

y = rand(size(x))

y = 1×13

0.9212 0.8744 0.2187 0.7557 0.2641 0.1259 0.0031 0.0706 0.5817 0.2496 0.2765 0.0463 0.8021

plot(x, y)
datetick('x', 'HH')

If so then the mistake would be that date numbers for datetick purposes are in days, so 0:2:24 would be 0, 2, 4, 6, ... 24 days, midnight each time

[Vikash Raj]

Thank you Walter but Im still unable to get the axis as needed.

[Vikash Raj]

when I use codes:

TFinal = datetime(Timestamp, 'inputformat', 'yyyy - MM -dd''T''HH:mm:ss''Z''', 'TimeZone', 'GMT');
plot(datenum(TFinal), Absolute_VTEC) 

Im getting the graps as. How can I lable in hours.

[Vikash Raj]

I have also tried this:

TFinal = datetime(Timestamp, 'inputformat', 'yyyy - MM -dd''T''HH:mm:ss''Z''', 'TimeZone', 'GMT');
plot(datenum(TFinal), Absolute_VTEC)
set(gca, 'XTick', [1:2:24], 'XTickLabel', rem([0:2:24]+0,24))
axis([1  23    0  51])
xlabel('Time (Hr)')

. Im getting the required axis but the graph is missng. Kindly need suggestions.

[Walter Roberson]

Have a look at

format long g
datenum(datetime('now'))

ans = 
          738430.033308973

so today is on the order of 738430 --> about 7.384e5 .

Your range is roughly

datestr([7.359e5; 7.382e5])

ans = 2×11 char array
    '28-Oct-2014'
    '13-Feb-2021'

so you have a range of roughly 6 1/2 years for your data, and you want a mark for that every 2 hours... so you want roughly

 6.5 * 365 * 12

ans = 
       28470

so like 27500 tick marks in a single graph. People generally cannot figure out letters that are less than 4 pixels plus a column of spaces, so you would need roughly

 275000*5

ans = 
     1375000

pixels. At 75 pixels per inch

 1375000/75 * 2.54 / 100

ans = 
          465.666666666667

so you would need a screen that was getting up to the order of 1/2 a kilometer wide.

[Vikash Raj]

Thank you Im getting the issue. So for now can you suggest me how I can isolated the Vtec data on monthly basis from each year with the respective time.

[Walter Roberson]

Monthly... so each plot should have between 28*12 = 296 and 31*12 = 334 hour ticks ? So barely possible to make out at anything less than 1500 pixels wide ?

[Vikash Raj]

Thank you for your help and suggestions.