How can I plot arrows on date time plot ?

I have datetime scale on x-axis and numeric values in Y-axis. And I want plot arrows like this

[Adam Danz]

This doesn't look like a datetime plot.

Are the x values actual datetime or duration values or are you proving numeric values that you're calling 'datetime'?

[Jeevan Kumar Bodaballa]

That plot was a sample and I have data which is datetime on x-axis.

Answer 1

[Adam Danz]

You can use annotation objects whose positions are defined in normalized figure space. That requires you to convert the end points from data units to normalized figure units which is done in the demos below. Critically, pay attention to the inline comments because once the conversion is done, you cannot change the position of the axes relative to the figure and you cannot change the axis limits. The offset variable determines the vertical space between the upper axis and the arrows. The arrowEnds variable defines the endpoints of the arrows.

Demo with duration values

fig = figure(); 
ax = axes('Units','Normalize');  % important: normalized units!
time = seconds(0:100:5000);
data = rand(size(time));
plot(time,data); 
grid(ax, 'on')

% Define start/stop of horizontal arrows in data units. 
arrowEnds = [1000, 2000;  2000,  4000]; % nx2 array of n [start, end] values.

% IMPORTANT
% set axis limits and add any legends and colorbars before proceeding!
% The axis should not change position relative to the figure after here.  
xlim(ax, [min(time), max(time)]) 
ylim(ax, ylim(ax))           

% Convert arrowEnds from data to normalized fig units
axPos = ax.Position; 
xl = seconds(ax.XLim); % Convert to numeric
yl = ax.YLim; 
arrowEndsAxisNorm = arrowEnds./range(xl) + xl(1);
arrowEndFigNorm = arrowEndsAxisNorm.*axPos(3) + axPos(1);
offset = 0.025;  % vertical offset from top of axes (normalized units)
yFigNorm = (sum(axPos([2,4])) + offset); 

% Add arrow annotations
ah = gobjects(1,size(arrowEndFigNorm,1)); 
for i = 1:size(arrowEndFigNorm,1)
    ah(i) = annotation(fig, 'doublearrow', arrowEndFigNorm(i,:), [yFigNorm,yFigNorm]);
end

Demo with datetime values

fig = figure(); 
ax = axes('Units','Normalize');  % important: normalized units!
time = datetime(1999,01,01) + days(1:10:500); 
data = rand(size(time));
plot(time,data); 
grid(ax, 'on')

% Define start/stop of horizontal arrows in data units. 
% nx2 array of n [start, end] values in datetime.
arrowEnds = [datetime(1999,04,01), datetime(1999,10,01); 
             datetime(1999,10,01), datetime(2000,04,01)];

% IMPORTANT
% set axis limits and add any legends and colorbars before proceeding!
% The axis should not change position relative to the figure after here.  
xlim(ax, xlim(ax)); 
ylim(ax, ylim(ax))           

% Convert arrowEnds from data to normalized fig units
axPos = ax.Position; 
xl = ax.XLim; 
yl = ax.YLim; 
arrowEndsAxisNorm = (arrowEnds-xl(1))/range(xl); 
arrowEndFigNorm = arrowEndsAxisNorm.*axPos(3) + axPos(1);
offset = 0.025;  % vertical offset from top of axes (normalized units)
yFigNorm = (sum(axPos([2,4])) + offset); 

% Add arrow annotations
ah = gobjects(1,size(arrowEndFigNorm,1)); 
for i = 1:size(arrowEndFigNorm,1)
    ah(i) = annotation(fig, 'doublearrow', arrowEndFigNorm(i,:), [yFigNorm,yFigNorm]);
end

[Jeevan Kumar Bodaballa]

This is my actual plot and I want to make xlines at three periods in the time series at certain dates and in between plots I want to mark the arrows. So can you please tell me how can I use your code to this plot.

[Adam Danz]

Why didn't you provide this as the example in your question? It would have same much time to provide an accurate example.

[Adam Danz]

I've updated my answer with a second demo using datetime values.