Ploting vs. 24hour day time (string that resets to zero and repeats)

I want to plot some data that looks like this( i.e, plot(time,x).

time= [ 12 14 16 18 20 22 0 2 4 6 8 10 12 14 16 18 20 22 0 2 4 6 8 10]

X= [ 30 32 34 30 29 26 22 20 18 19 20 28 30 32 34 30 29 26 22 20 18 19 20 28]

but looking for best way to keep order of the data as is. Currently I split the data between 0 times and plot on adjacent subplots which looks ugly. Any suggestions appreciated.

Answer 1

[Star Strider]

I suspect this may be what you want to do:

time = [ 12 14 16 18 20 22 0 2 4 6 8 10 12 14 16 18 20 22 0 2 4 6 8 10];
X = [ 30 32 34 30 29 26 22 20 18 19 20 28 30 32 34 30 29 26 22 20 18 19 20 28];
xt = 1:length(time);                                % X-Ticks

figure(1)
plot(xt, X)
grid
set(gca, 'XTick', xt, 'XTickLabels', time)          % Label X-Axis With ‘time’ Vector

Apologise for the delay — hardware crash on my primary MATLAB computer a couple hour ago, so had to install new to this one.

[dpb]

That's a good point I tend to forget, Star; that 'ticklabels' property will convert the numeric to string automagically...so the difference between the two is the formatting of the labels; this way they're numeric representation with variable width, with the datenum and using datetick they're treated as dates and have a fixed-width field (ie, '02' instead of '2').

[Sina Shojaei]

Thanks.silly me ;)

[Star Strider]

My pleasure!

Not silly — it may not be something you would have likely encountered unless you read the documentation on ‘handle graphics’ in some detail.

Answer 2

[dpb]

A) Convert times to a datenumber and plot against it instead. Use datetick to format the axis or use the new time class with builtin support in latest release(s), or

B) Plot versus index instead of actual time and set tick mark labels manually -- not particularly elegant so A) is the better option.

dn=datenum(2015,1,1,12+[0:2:2*length(time)-1].',0,0);
plot(dn,X)
xlim([dn(1) dn(end)]), ylim([15 35])
datetick('x','dd-HH','keeplimits')

Above uses arbitrary start date; it's immaterial to simply show times but datenum needs six values. Note the generation of the two-hour increments from the starting point to match the length of the data vector and that plotting is against the date numbers that are monotonic which solves your problem of "what to plot against?".

As noted, there's a new time class but I don't have latest release so can't demonstrate it...