hold on y-axis

i want to plot axes parallel to y-axis. I got the limits for y easily and

on the x-axis I have dates like '2020-11-17 13:03:00'.

this is my plot

figure
yyaxis left 
plot(T.UTC_Date___Time,mareaCM,'b--');
ylim
yyaxis right
plot(T.UTC_Date___Time,T.DissolvedOxygenSaturation,'r--');
hold on
%I tried with this but it doesn't work
plot([2020-11-17 13:03:00 2020-11-17 13:03:00],[0 450],'g--')

[Andy]

Do any error messages appear or is it that Matlab doesn't report a problem but the line doesn't appear where you think it should?

Answer 1

[Steven Lord]

%I tried with this but it doesn't work
% plot([2020-11-17 13:03:00 2020-11-17 13:03:00],[0 450],'g--')

No, that's not going to do what you expected. If you want to plot using date and time data on the X axis, turn that data into a datetime array first.

s = ['2020-11-17 13:03:00'; '2020-11-17 13:03:00']

s = 2×19 char array
    '2020-11-17 13:03:00'
    '2020-11-17 13:03:00'

dt = datetime(s)

dt = 2×1 datetime array
   17-Nov-2020 13:03:00
   17-Nov-2020 13:03:00

In this case using the xline function is probably what you want instead of plotting using the same X values twice. That will keep the line spanning the whole height of the axes even if you pan or change the Y axis limits.

xline(dt(1), 'g--')

[GIOVANNA GUADAGNIN]

thank you!