I have recorded data for 24h with frequency 4hz, so I have 4 values per second. The following time stamp in example is: 17:23:21:000 (HH:mm:ss:SSS). I want to import time data in matlab so, that in plot on x axis it shows as minutes not this long times stamp example. Can someone explain me how? Thank you!
You can use datetick to make your axis show formatted datetimes:
datetick(gca,'HH:mm')
Related
I'm trying to plot some data with respect to minutes instead of seconds in Matlab as formatted time, i.e. min.sec.
I have real time data streaming in where with every sample received, its time in seconds is also sent. I then plot them with respect to time. Now, since my session is around 15 minutes long, I can't be plotting with respect to time. Therefore I wanted to plot it with respect to time (min.sec). I tried dividing the received time by 60 but this gives me minutes with 100 subdivisions instead of 60 (the minutes increment after 0.9999 instead of 0.59). How do I convert it so that I'm able to plot with respect to time in minutes?
Here is what I mean by 0.99 fractions of a minute instead of 0.59. A normal minute has 60 divisions not 100.
EDIT:
I tried m7913d's suggestions and here is what I got.
first I plot the signal with respect to time in seconds without changing the ticks ( A normal plot(t,v))
The I added datetick('x', 'mm:ss'); to the plot (Xtick format is not supported in Matlab 2015b)
Here is a screenshot of the results
The time in seconds was up to 80 seconds, when translated into minutes, it should give me 1 minutes and 20 seconds as the maximum x axis limit. But this is not the case. I tried to construct a t vector (i.e like t=0:seconds(3):minutes(3)) but I couldn't link it to my seconds vector which will be constantly updating as new samples are received from the serial port.
Thanks
You can use xtickformat to specify the desired format of your x labels as follows:
% generate a random signal (in seconds)
t = 0:5:15*60;
y = rand(size(t));
plot(seconds(t),y) % plot your signal, making it explicit that the t is expressed in seconds
xtickformat('mm:ss') % specify the desired format of the x labels
Note that I used the seconds methods, which returns a duration object, to indicate to Matlab that t is expressed in seconds.
The output of the above script is (the right image is a zoomed version of the left image):
Pre R2016b
One can use datetime instead of xtickformat as follows:
datetimes = datetime(0,0,0,0,0,t); % convert seconds to datetime
plot(datetimes,y)
datetick('x', 'MM:SS'); % set the x tick format (Note that you should now use capital M and S in the format string
xlim([min(datetimes) max(datetimes)])
I have the following values in Excel:
Bed time 19:34:00
Get up time 07:04:00
Time in bed 11:30:00
Sleep start 19:42:00
Sleep end 07:00:00
I want to import them into MATLAB and do some calculation on these time values such as subtraction. The time values look like this after importing:
0.8153
0.2944
0.4792
0.8208
0.2917
and obviously doing calculation on them would be nonsense. Would any body help me with this issue? I have stuck with it for few days, and no progress yet.
Thanks in advance,
As assylias pointed out, these are fractions of days. You can use the datestr function to convert it to human-readable strings with formatting option conveniently.
e.g.:
datestr(0.2917, 'HH:MM:SS')
ans =
07:00:02
Calculations such as subtractions can be done on the raw values before
conversion.
E.g: get duration of sleep.
start = 0.8208
stop = 0.2917
datestr(stop-start, 'HH:MM')
ans =
11:18
Even works for intervals that span over midnight.
I have voltage and current signals from multiple days. The time vector is in seconds of the day (SOD), and the voltage and current vectors are in volts and amps respectively. However, the vector data from each day is different lengths. For example Mondays data might be 1x100000 for both time and voltage/current, and Tuesdays might be 1x50000 for both time and voltage/current. I was asked to plot the different days of data on the same figure for comparison purposes. I have tried using the plot(x1,y1,x2,y2) method but that obviously didn't work due to different vector lengths. I tried interpolating to the larger data set, but then realized that I will get all NaNs on the result since there is no overlap in time. I ran out of ideas and am desperately in need of help.
EDIT:
I guess I forgot to mention that somehow I would like to overlay them one on top of the other in the same figure and not using a subplot.
It sounds like you want a data vector of length n to span, I'm guessing, 24 hours = 86400 seconds, for any n (e.g. n=100000 or n=50000). Assuming the original data is uniformly sampled, this should do the trick:
x1=linspace(0,86400,length(x1));
x2=linspace(0,86400,length(x2));
plot(x1,y1,'r-',x2,y2,'b-');
If it is not uniformly sampled, we can still make it work:
t1=linspace(0,86400,length(x1));
t2=linspace(0,86400,length(x2));
newy1 = spline(x1,y1,t1);
newy2 = spline(x2,y2,t2);
plot(t1,newy1,'r-',t2,newy2,'b-');
I created a diagram presenting limb movement over the time (2.56 seconds). My diagram looks like in the top Picture 1.
My code to get the diagram was:
x=data(1000:1256,2)
Fs=100
Ts=1/Fs
L=length(x)
t = (0:L-1)*Ts;
figure
plot(t,x);
Now Im trying to change time units into real time data (day and time, when the measurements were recorded), I want to get something like in the Picture 2: mark x-axis with date and time. Ideally Id like to have 6 time marks.
Using:
datestr(data(1000),'dd-mm-yyyy HH:MM:SS AM')
I know the first time (row 1000th of my data) is 10-07-2010 11:31:50 PM and the last row (1256th) is 10-07-2010 11:43:42 PM. There was always 50 records recorded per 1 second, BUT the problem is, the measurements were not recorded constantly - I mean, sometimes there was no measurements for a few minutes (when there was no movement).
I ve been trying to use XTick etc but I dont know how to select the real-time data for my x-axis and how to label x-axis with the real time of measurements.
labels=datestr(data);
set(gca,'XTick',1:6; 'XTickLabel',labels);
Anybody could help me?
This should format the tickmarks
datetick('x', 'dd-mm-yyyy HH:MM:SS AM')
It might go after setting the tickmarks
set(gca,'XTick',[ ... ])
Where in the array you should put the datenum values of your times.
Consider this minimal example:
x = linspace(now-2, now, 30);
y = rand(30, 1);
plot(x, y)
datetick('x', 'dd-mmm HH:MM')
I am new to Matlab. I am trying to use datenum function to parse date string and convert to timestamps(like in Java, getTime()).Then, I want to find out the difference between two dates in seconds.
datenum('2013-02-21T00:39:19Z','yyyy-mm-ddTHH:MM:ss')-datenum('2013-02-21T00:34:19Z','yyyy-mm-ddTHH:MM:ss')
If I run the function above, I get 0.0035 which I have no idea what kind of value it is.
Can someone help please?
Thanks!
Matlab help says:
A serial date number represents the whole and fractional number of
days from a fixed, preset date (January 0, 0000).
I reckon your answer is maybe 0.0035 days so to get seconds I guess its
ans*24*60*60
Your result is in datenum format as Dan says. But if you want to find elapsed time in seconds, there is a function that does exactly what you want.
You can use etime to find elapsed time between two date vectors.
d1 = datevec('2013-02-21T00:39:19Z','yyyy-mm-ddTHH:MM:ss');
d2 = datevec('2013-02-21T00:34:19Z','yyyy-mm-ddTHH:MM:ss');
elapsedTime = etime(d1,d2) % Elapsed time in seconds
elapsedTime =
300