How to plot some xtickslabel that correspond to y data?

Hello!

I've read a lot of answers about xticklabel and datetick, but i'm very confusing yet.

I have two vectors of 30 points.

y = 30 points 
x = 30 points type date string (i've used datestr() from a datenum() number) (HH:MM:SS.FFF). See like this:

' 06:22:19.041'
' 06:22:19.048'
' 06:22:19.050'
' 06:22:19.055' ...

I used the plot function only for the y data:

plot(y);

The x data on the graphic was = 1...5...10...15...20...25...30. (7 numbers!)

So, i changed the xtickslabels:

set(gca, 'XTickLabel', x);

And the xtickslabels changed for the only the first 7 numbers of my x vector.

I need plot few points, as i did, but the points on xticks have to correspond to the y data.

Thanks. Sorry about the language

Answer 1

[Walter Roberson]

set(gca, 'XTick', 1:length(x), 'XTickLabel', x);

[Arthur]

Thanks a lot, Walter!

But can i plot less points on the X ticks? I can't get a clean vision. See my problem on the image link

https://www.dropbox.com/s/stgth5hjf9wk51i/evento_agregado_1.jpg

[Walter Roberson]

I suggest you take a different approach.

Let xdatenums be the datenum values, not converted to strings. Then,

plot(xdatenums, y);
datetick( 'x', 'HH:MM:SS.FFF');

[Arthur]

Ok. I tried it once, but when i use plot(xdatenums, y), the numbers are so big that:

K>> f = datenum(t_event_agreg{i,1},'HH:MM:SS.FFF')

f =

    1.0e+005 *

      7.3487
      7.3487
      7.3487
      7.3487
      7.3487

And the figure is shown as the link below

https://www.dropbox.com/s/stgth5hjf9wk51i/evento_agregado_1.jpg

A part of my code is:

f = datenum(t_event_agreg{i,1},'HH:MM:SS.FFF');

figure(i)

hold;

plot(f,v_fase_a_evento_agreg{i,1},'LineWidth',2, 'Color','r'); 
plot(f,v_fase_b_evento_agreg{i,1},'LineWidth',2, 'Color','bl');
plot(f,v_fase_c_evento_agreg{i,1},'LineWidth',2, 'Color','k');

datetick('x', 'HH:MM:SS.FFF');

grid minor;
title(['Evento Agregado n.: ',num2str(i)])
xlabel ('Tempo [MM:SS.FFF]');
ylabel ('Magnitude da Tensão de Fase [%]');
ylim([0 120]);
legend('Fase A','Fase B','Fase C')

Thank , one more time

[Walter Roberson]

Don't worry about how big those values for f are. You might want to give the command

format long g

to read them more naturally.

Do not issue the "hold" until after you have done the first plot.

[Arthur]

Its a wrong plot yet! :(

https://www.dropbox.com/s/stgth5hjf9wk51i/evento_agregado_1.jpg

[Walter Roberson]

That appears to be the same URL as before you moved the "hold"

f = datenum(t_event_agreg{i,1},'HH:MM:SS.FFF');

figure(i)

plot(f,v_fase_a_evento_agreg{i,1},'LineWidth',2, 'Color','r'); 

hold on          %moved to here!

plot(f,v_fase_b_evento_agreg{i,1},'LineWidth',2, 'Color','bl');
plot(f,v_fase_c_evento_agreg{i,1},'LineWidth',2, 'Color','k');

datetick('x', 'HH:MM:SS.FFF');

grid minor;
title(['Evento Agregado n.: ',num2str(i)])
xlabel ('Tempo [MM:SS.FFF]');
ylabel ('Magnitude da Tensão de Fase [%]');
ylim([0 120]);
legend('Fase A','Fase B','Fase C')

[Arthur]

yes Walter, is the same url because i erased the figure and 'run' the code again. I moved the 'hold'. See:

 f = datenum(t_event_agreg{1,1},'HH:MM:SS.FFF')

f =

           734869.26549816
          734869.265498218
          734869.265498264
           734869.26549831
          734869.265498356
          734869.265498403
          734869.265498449

 v_fase_a_evento_agreg{1,1}

ans =

                      99.1
                      99.1
                      99.2
                      99.1
                        99
                      99.1
                      99.1

I guess that the commands plot(f,v_fase_a_evento_agreg{1,1}) visually in plot area isn't possible to see. The axis do not appear to be automatic adjusting. I think!

[Walter Roberson]

Interesting! The lower level graphics are imposing a minimum distance between xlim boundaries of approximately 1/6000 whereas your data is many times finer grained than that. setting xlim manually did not help, even with XLimMode set to 'manual': the graphics overrides it.

So....

dv = datevec(f);
x = dv(:,6);
plot(x, y)

The result will be in milliseconds (only), corresponding to the fact that your data values are a fraction of a millisecond apart. If you want to include seconds, you can make a calculation such as

x = dv(:,5) + dv(:,6)/ 1000;

but be warned that your f are close enough together that the tick labels might not all be different. It is possible to increase the precision of the tick labels with

set(gca, 'XTickLabel', num2str(get(gca, 'XTick').', '%.6f'))

[Arthur]

I did some tests here. I realy thank your help.

In some plots, the seconds, miliseconds and the minutes are changing. i want to plot the x axis in MM:SS.FFF format. So guess only the strings will do it to me.

Can you plot on x axis a string vector 'dateticks' and erase some data to improve the visualization? Replacing some data to a blank ' '?

This graphics will be a part of an research article and the reviser suggested that i should do in this way... :s. I'm sending here the two complete vectors to plot.

K>> v_fase_a_evento_agreg{1,1}

ans =

                      99.1
                      99.1
                      99.2
                      99.1
                        99
                      99.1
                      99.1
                      99.1
                      99.1
                      99.2
                      99.1
                      99.1
                        99
                      98.4
                      98.5
                      98.4
                      98.2
                      99.1
                      99.4
                      98.6
                      98.5
                        99
                      99.1
                      98.6
                      98.4
                      98.9
                      99.1
                      98.8
                      98.5
                        99

K>> t_event_agreg{1,1}

ans =

    ' 06:22:19.041'
    ' 06:22:19.046'
    ' 06:22:19.050'
    ' 06:22:19.054'
    ' 06:22:19.058'
    ' 06:22:19.062'
    ' 06:22:19.066'
    ' 06:22:19.071'
    ' 06:22:19.075'
    ' 06:22:19.079'
    ' 06:22:19.083'
    ' 06:22:19.087'
    ' 06:22:19.088'
    ' 06:22:19.096'
    ' 06:22:19.097'
    ' 06:22:19.104'
    ' 06:22:19.108'
    ' 06:22:19.112'
    ' 06:22:19.116'
    ' 06:22:19.121'
    ' 06:22:19.125'
    ' 06:22:19.129'
    ' 06:22:19.133'
    ' 06:22:19.137'
    ' 06:22:19.141'
    ' 06:22:19.145'
    ' 06:22:19.150'
    ' 06:22:19.154'
    ' 06:22:19.158'
    ' 06:22:19.162'

[Arthur]

Walter,

I found a solution for now, but a manual solution. plot(y); f=datestr(t_event_agreg{1,1},'HH:MM:SS.FFF'); set(gca,'XTick',1:length(f),'XTickLabel', f);

So i went to figure properties /Ticks and erase some LABELS keeping the locations. It is my solution for only one graphic.

after, I used this command to check:

get(gca,'Xticklabel') ans =

    '06:22:19.041'
    ''
    ''
    ''
    '06:22:19.058'
    ''
    ''
    ''
    ''
    '06:22:19.079'
    ''
    ''
    ''
    ''
    '06:22:19.097'
    ''
    ''
    ''
    ''
    '06:22:19.121'
    ''
    ''
    ''
    ''
    '06:22:19.141'
    ''
    ''
    ''
    ''
    '06:22:19.162'

How can i modify the orginal vector of time e fill it with 'blanks'???