MATLAB: How to change number of tickmarks for dateaxis

datedateaxisplottick marksx axis

Hey everyone,

I am trying to plot a time series that consists of 8760 data points with a value for each hour of the year. I want to show the values in the plot and display the months of the year on the x axis. I found the function dateaxis which seemed pretty easy, but matlab only displays four months of the year… I want all twelve…

Is there a way to tell dateaxis how many months to plot? If there is not, can you tell me a different way on how to plot my time series??

Thanks a lot!

Best Answer

This works to plot months:

x = 0:8759;
y = sin(2*pi*x/(24*30.5));          % Something To Plot
xd = datenum([2014 01 01]) + x/24;
figure(1)
plot(xd, y)
set(gca, 'XTick', 0:11)
datetick('x', 'mmm')
axis tight

Your ‘xd’ and ‘y’ will be different but my set and datetick calls should work.

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MATLAB: Are the dates not aligned correctly when I use the DATEAXIS function

The DATEAXIS function is performing as expected, as it does not have the feature of placing the year labels at the beginning of the year. This is because the DATEAXIS function simply replaces axis tick labels with date labels.

The axis tick labels are originally in numeric format and so do not actually represent beginnings of the years. So, after the labels have been replaced they do not actually represent the beginnings of the years.

 If you want the year labels to mark the beginnings of the years, a better function to use is DATETICK. For more information regarding this function enter
    doc datetick

at the MATLAB Command Prompt.

MATLAB: Place annotations using axis coordinates from a date-axis

A start...basically, you just generate datenums that match the locations you want.

dt=datenum(2014,5,[10:12]);           % datenums for the day tick locations
xt=repmat(dt,3,1); xt=xt(:);          % and make an array of x and y locations
xt(3:3:end)=nan;                  % insert nan to break lines between locations
yt=repmat([-0.95 -1.1 nan]',3,1);     % to draw the lines at those locations (*)
hl=line(xt,yt,'color','r','clipping','off');  % lines; made red so stand out
% write the text.
ht=text(dt+0.5,-1.2*ones(size(dt)),datestr(dt,'mm.dd.yyyy'),'horizontal','center','fontsize',8);

(*) The "trick" in generating the arrays is that of inserting the NaN between the line segments to avoid drawing from the end point of the first the diagonal to the first point of the second, etc., ...

On the location for the datestr, I didn't create the other vector of locations; just used the midnight location plus 0.5 day to get noon next day for demo purposes of the idea. That works correctly for the full days in the middle, otherwise you take the average of the two datenums for the beginning and end of the partial days at the two ends.

Also, in my playing here I used a ylim(-1 1)] and the y locations for the line and the text are based on that value--you'll want to retrieve the lower y limit and adjust based on it for your case. Alternatively, you can switch to normalized coordinates relative to the whole figure and retrieve the position of the axes and work out locations therefrom. annotation works on those coordinates so if choose to go that route instead you'll have to use those. I tend to just use the axes and smudge a little. Note to get the line to show outside the axes, must set its 'clipping' property to 'off'

Best Answer

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MATLAB: Are the dates not aligned correctly when I use the DATEAXIS function

MATLAB: Place annotations using axis coordinates from a date-axis

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