Axis date values disappear when datetick is applied to a simple time-series plot

조회 수: 3 (최근 30일)
Hello,
I'm creating a plot of time (x-axis) against flow rate (y-axis). Time is displayed in decimal format and I want to convert this to real dates in the format dd/mm. To do this I am using datetick, which normally works for me, but the result in this instance is that all values on the x-axis are removed with the exception of the first and last values (which are converted to dd/mm format). Seems simple.
figure; plot(Time,flowrate,'r.'); datetick('x','dd/mm');
Any suggestions to what I might be doing wrong would be greatly appreciated.

채택된 답변

Harry MacDowel
Harry MacDowel 2011년 9월 7일
I feel your pain. I used to deal with date on x-axis and it is really a huge, huge pain.
I suggest you go to File Exchange and grab the function called: xticklabelrotate
That function can actually rotate your x-axis at any angle you want. For dates, I go for a 90 degrees rotation.
Using datetick straight away will create a lot of problems. For me, I am tired of doing that so I experimented my own way. Somehow I achieved great feats with the following procedure:-
1) Convert your time matrix into strings using datestr BEFORE you plot it. Or below I provide my way of doing it which is doing it on the spot. Change the codes the way you want;
2) Determine how many x-ticks you want. If you want 21 x-ticks, then generate a so-called spaceData as follows:-
spaceData = linspace(1,x_lim,20);
spaceData = round(spaceData);
Here my x_lim is the last of my Time matrix. It is acquired by:-
x_lim = length(time);
3)Then create the xData:-
for i=1:20
xData(i) = cellstr(datestr(time(spaceData(i))));
end
What I am doing here is changing the time value at the locations notified by spaceData into strings. Then 'trap' them into cellstring.
4)And then I generate the following two matrices:
xdata_gen = zeros(x_lim,1);
for i=1:x_lim
xdata_gen(i) = i;
end
Mind that x_lim here is not 21 but the length of the time matrix. What I am doing here is generating the exact number of xdata_gen elements as that of the variable time.
xdata_gen is just a number matrix from 1,2,3,4,5......x_lim
5. Here comes the magic:-
hl1 = bar(xdata_gen,y);
ax1 = gca;
set(gca,'color','white'); % sets the color to white
set(gca,'Box','off'); % here gca means get current axis
set(gca,'TickDir','out');
set(gca,'XTick',spaceData,'XTickLabel',xData,'XMinorTick','on','YMinorTick','on','XLim',[0 x_lim])
xticklabel_rotate;
So the trick is to plot the numbered matrix against y (or your flowrate, then tell Matlab that you only want 21 ticks and their positions on x-axis.
After that change all the numbers into the cellstr date matrix.
After that rotate the x-axis labels.
Sounds a little complicated but it really works.
Good luck!
  댓글 수: 3
Oleg Komarov
Oleg Komarov 2011년 9월 7일
It doesn't need to be so complicated as I shown below. Please read also my comment below.
Harry MacDowel
Harry MacDowel 2011년 9월 7일
No worries Saul. Hope it really helps. =)
The magic of my method is the fact that you can project it to plot multiple x-axis but only show the date and not double x-axis.
You can create a matrix equivalent to the length of time matrix called emptyData in which all are the cellstr(' ')
Pad the emptyData onto the newly laid over x-axis of the plot.
Cheers!

댓글을 달려면 로그인하십시오.

추가 답변 (1개)

Oleg Komarov
Oleg Komarov 2011년 9월 7일
Get used to set the properties for your plots, especially when you start adding a little bit of customization. My plots sometimes take the whole screen and I am not doing anything special apart from setting labels, ticks and manually subplotting.
An example:
time = now-99:now;
flow = cumsum(randn(100,1));
plot(time,flow,'r')
datetick('x','dd/mm');
% Set Xlim and ticks position
set(gca, 'Xlim',time([1,end]),'Xtick',linspace(time(1),time(end),9))
  댓글 수: 2
Saul
Saul 2011년 9월 7일
Thanks Oleg, for some reason this didn't work with my plot, it adds the extra dates as needed but the only two dates are replicated 9 times.
Thanks anyway
Oleg Komarov
Oleg Komarov 2011년 9월 7일
Without the actual data is hard to guess what is happening. I would be interested to know what your times is.

댓글을 달려면 로그인하십시오.

카테고리

Help CenterFile Exchange에서 Line Plots에 대해 자세히 알아보기

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by