如何在MATLAB或Octave中的x轴上绘制日期时间

Question

In MATLAB or Octave, my data has the following format for date/time values:

12:00:34.626 AM 2/26/2017

where it is HH:MM:SS:SSS [A or P]M [M]M/DD/YYYY

I want to use it for my x-axis on my plots, and I have tried using datetick , datenum , and datestr and haven't been able to get any of them to work with this format.

How can I use this formatted value string to label my x-axis datapoints?

Answer 1

I would use a combination of these functions, namely datnum followed by datetick after plotting.

First off your formating string need to be: 'HH:MM:SS.FFF AM mm/dd/yyyy'.

See the following if you need to change format: https://au.mathworks.com/help/releases/R2016b/matlab/ref/datenum.html#inputarg_formatIn

Then use datetick to convert to nice format on plot. https://au.mathworks.com/help/releases/R2016b/matlab/ref/datetick.html

So to a single data point= plot you might have:

xdatestr=['12:00:34.626 AM 2/26/2017'; '12:00:34.626 PM 2/26/2017']
xdatenum=datenum(xdatestr,'HH:MM:SS.FFF AM mm/dd/yyyy')
plot(xdatenum,[0 1])
datetick(gca)

Also note datetime , is whole seperate way of doing it, and uses a different format string convention. http://au.mathworks.com/help/matlab/ref/datetime.html

Answer 2

You can use the following format:

d = datetime('12:00:34.626 AM 2/26/2017','InputFormat','hh:mm:ss.SSS a M/dd/yyyy')

result:

d = 
   26-Feb-2017 00:00:34

and if you want to see also the fractions of a second:

>> d.Second
ans =
       34.626

For multiple dates strings, stored in a cell array, just replace the string '12:00:34.626 AM 2/26/2017' above with the cell array.

Then you just write plot(d,y) (where y is your data) and you get the x-axis in a time format. You can further customize this format by using the DatetimeTickFormat property:

plot(d,1,'DatetimeTickFormat','hh:mm:ss.SSS a M/dd/yyyy')

And you will get:

see also here and here .

Answer 3

Another example is this.

date={'12:00:34.600 AM 2/26/2017','12:00:34.700 AM 2/26/2017','12:00:34.800 AM 2/26/2017','12:00:34.900 AM 2/26/2017'};
timeFormat='HH:MM:SS.FFF AM mm/dd/yyyy';
xdatenum=datenum(date,timeFormat);
data=0:3;
plot(xdatenum,data)
datetick('x',timeFormat,'keepticks')
view([-20,90])

I tilted the plot a little to avoid overlap of x ticks.

You can control the number of ticks by using tick properties.

date={'12:00:34.600 AM 2/26/2017','12:00:34.700 AM 2/26/2017','12:00:34.800 AM 2/26/2017','12:00:34.900 AM 2/26/2017'};
timeFormat='HH:MM:SS.FFF AM mm/dd/yyyy';
xdatenum=datenum(date,timeFormat);
data=0:3;
plot(xdatenum,data)
datetick('x',timeFormat,'keepticks')
set(gca,'XTick',[min(xdatenum) max(xdatenum)])
set(gca,'XTickLabel',[date(1),date(end)])

Here, I made just two ticks with minimum date and maximum date.