how to write in the middle of ticks?

Hello Everybody.

I have a graph with my major ticks setted on 1 Janauary of each Year. I want to be able to write the year in the middle, so using I guess a Minortick and as it was set at June of each year. And of course, i would like to delay the xticklabels

I cannot understand honestly how to do, in the massive jungle of minorticks and ticks.

Thank you for your helping in advance!

Answer 1

[Adam Danz]

Datetime x-ticks for 6-month intervals

It looks like you want to set xtick, not minor ticks.

If your data are in datetime format and you want half-year ticks on January 1st and July1st for every year,

% dt is your datetime vector.
% Create vector of Jan 1st /July 1st dates spanning the range of your data.

startDate = dateshift(min(dt), 'start', 'year'); 
endDate = dateshift(max(dt), 'start', 'year') + calyears(1);
dtTicks = startDate : calmonths(6) :  endDate; 

% set ticks
set(gca, 'XTick', dtTicks, 'xlim', dtTicks([1,end])) % xlim optional

You can edit for datetime tick format using

datetick('x','mmm-yy','keeplimits','keepticks')
% or 
datetick('x','QQ-yyyy','keeplimits','keepticks')

Demo

dt = datetime(2005,03,16) + caldays(0:20:1000);
data = (0:20:1000).^2; 
plot(dt, data, 'o')

To place labels between ticks

Since Matlab does not support minor-tick labels, and since we cannot specify the position of a tick label independently from the tick positions, you'll have to use a workaround.

One workaround is to use text objects as xtick labels but that gets sloppy when the figure is resized or the axis limits are changed.

Another workaround is to add a 2nd underlying axis that controls the xtick labels while the main axis controls the xticks. That's demonstrated below. See inline comments for details.

% Create demo data
dt = datetime(2005,03,16) + caldays(0:20:3000);
data = (0:20:3000).^2; 

% Create main axis and an underlying axis to control xticklabels.
axUnder = cla(); % Underlying axis handle
ax = copyobj(axUnder, ancestor(axUnder,'figure')); % main axis handle.

% Plot data on main axis (ax)
plot(ax, dt, data, 'o')

% Compute start|end date, both on Jan 1 of some year
startDate = dateshift(min(dt), 'start', 'year'); 
endDate = dateshift(max(dt), 'start', 'year') + calyears(1);

% Compute 6-month interval date ticks
dtTicks = startDate : calmonths(6) :  endDate; 

% Set xticks of the main axis to Jan 1st of each year but remove labels
xticks = dtTicks(1:2:end);
xtickLabs = repmat({' '},size(xticks)); % to get the xlabel spacing right
set(ax, 'XTick', xticks, 'XLim', [min(dtTicks),max(dtTicks)],'XTickLabel', xtickLabs)

% Set xticks of underlying axis to July 1st of each year, use Jan 1st tick labels
% We also need to plot an invisible data point on the underlying axis to force the 
% xaxis to be datetimeruler.
plot(axUnder, dt(1), nan, 'x') % will not appear.
dtTicksLabs = cellstr(datestr(dtTicks(1:2:end),'yyyy')); 
set(axUnder, 'XTick', dtTicks(2:2:end),'XTickLabel', dtTicksLabs, 'xlim', ax.XLim)
axUnder.YTick = []; 

% Set title and axis labels
title(ax, '9-year trends')
xlabel(ax, 'Years')
ylabel(ax, 'stuff (units)')

% Equal axes positions and xlim so fig-resize doesn't mess things up.
% Must come after converting axUnder to datetimeruler. 
linkprop([ax,axUnder],{'Position','InnerPosition','XLim'}); % add more as needed
axUnder.HandleVisibility = 'off';  % avoid accidentally accessing the underlying axis

[Adam Danz]

fransec's answer moved here as a comment

Hei, thanks for answer.

Sorry, I didn't explain myself properly.

I want just to have major ticks, without labels, on each 1st January, and the label (i.e., "2013"), in between, but without tick, as I showed in this figure.

[Adam Danz]

I've updated my answer to address the problem you described.

[fransec]

Really cool, thank you a lot!

I didn't yet understood completely what you have done in each step, with it seems absolutely proper! ;) Now i am gonna deeper on your coding!

Thanks!

[Adam Danz]

Glad I could help. Let me know if you've got any Qs.

[Corymbiamaculata]

Not the OP, but I'd like to thank you for this answer - super helpful!

I would also like to ask a question :) Your code works perfectly with a single data series, but I haven't managed to make it work with two (or more). Despite using 'hold on', the first data series is now shown in the plot. The same happens with bar plot (which is what I'm trying to make).

plot(ax, dt, data1, 'o')
hold on
plot(ax, dt, data2, 'o')

I'd be grateful for advice on how to solve this. If that helps, I'm using Matlab 2020a. Thank you!

[Adam Danz]

@Corymbiamaculata thanks, the answer is a decent workaround at best. As you're discovering, it's not flawless. You've correctly used the ax handle in your plotting functions - this correctly specifies that you want your lines to appear in the ax axes. But you haven't specified which axes to hold and this is what's causing the problem.

Replace

hold on

with

hold(ax,'on')

[Corymbiamaculata]

Thank you!! Great to know I can use the 'hold' function this way.