Xticks as Days for specific data points

Dear all,

I am computing Value at Risk estimates for different time horizons and I would like to plot them against regular days. I know that you can specify the ticks of the x-axis somehow via datetime, but i don't seem to get the syntax correctly. You can see my code below.

I calculated different VaRs for 10, 30, 125 and 250 days and plot those data points against those 250 days, but I only manage to do that evenly spaced (e.g. same space between 10 and 30 and 30 and 125) which is obviously wrong.

set(gca,'XTick',datetime(1,1,250),'Xticklabel',[10 30 125 250])

Any help would be highly appreciated.

Leo

Answer 1

[Steven Lord]

Something along the lines of that code should work if you plotted your data with datetime X data.

daysSinceJanuary1st = randi([0 364], 1, 10)

daysSinceJanuary1st = 1×10

104 26 143 299 28 272 344 295 69 213

x = datetime(2021, 1, 1) + days(daysSinceJanuary1st)

x = 1×10 datetime array
   15-Apr-2021   27-Jan-2021   24-May-2021   27-Oct-2021   29-Jan-2021   30-Sep-2021   11-Dec-2021   23-Oct-2021   11-Mar-2021   02-Aug-2021

h = plot(x, 1:10);

xticks(datetime(2021, 1:12, 1))
xlim(datetime([2021, 2022], 1, 1))

If you want to customize the ticks or the tick labels further, you may need or want to work with the ruler for the X axis directly.

theAxes = ancestor(h, 'axes');
theRuler = theAxes.XAxis

theRuler = 
  DatetimeRuler with properties:

             Limits: [01-Jan-2021    01-Jan-2022]
         TickValues: [01-Jan-2021    01-Feb-2021    01-Mar-2021    01-Apr-2021    01-May-2021    01-Jun-2021    01-Jul-2021    01-Aug-2021    01-Sep-2021    01-Oct-2021    01-Nov-2021    01-Dec-2021]
    TickLabelFormat: 'MMM'

  Show all properties

[Leonard Meyer]

Thanks so far, but that doesn't seem to work for me. Maybe datetime is not suitable for what i'm looking for. I just need 250 days (or time increments) on the x axis and then I would like to match 10, 30, 125 and 250 with my calculated VaR estimates.

Do you have any suggestions for that?

Thank you!