How to add a vector of seconds to time HH:mm:ssPM in MATAB?
I usually have this nice way in Excel to convert normal number format to hour and minutes and sec. format using simple cell custom formatting, but when I put down code below in MATLAB, instead of incrementing in seconds, it adds in days!
time = 1+0:50000+0; % sec
% To show date as plot label it should be converted from numbers to letters
hr_matlab = time' + datenum('4:10:44 PM');
hr= datestr(hr_matlab, 'HH:MM:ssPM');
figure(222)
plot(hr,S,'-b','LineWidth',2)
I am using MATLAB2014a and don't have access to function datetime.
datenum converts the date to a number that represents days as whole numbers. For that reason, when you add the vector [1,2,3,...], you acturally add days to your fixed time ('4:10:44 PM').
if you want to add it as seconds, you need to divide time in the amount of seconds per day:
hr_matlab = (time')/86400 + datenum('4:10:44 PM');
One simple option is to add two date numbers:
hr_matlab = datenum('4:10:44 PM') + datenum(0, 0, 0, 0, 0, time.');
Related
I have 2 times stored in character arrays in MATLAB.
a = '11:00 PM'
b = '07:30 AM'
I want to find the difference in hours between the 2 times, which should be 8.5 hours in this example. Is there any short method to do that? I can datenum both numbers, subtract them, datevec the difference, extract the hours and minutes from the vector, and convert them into hours, but this takes a lot of lines. Is there a more efficient way of doing this or is there an existing function?
You can do this by converting each string using datetime, taking the difference, then converting the result with hours:
numHours = hours(diff(datetime({a; b}, 'InputFormat', 'hh:mm a')));
numHours = numHours + 24.*(numHours < 0)
numHours =
8.5000
The second line accounts for the condition in your example, where the second time has to occur on the next day for the time difference to be positive, so 24 hours are added to the (negative) difference.
add a date to the time
like
a = '1/1/2000 11:00 PM'
b = '1/1/2000 07:30 AM'
the convert the string to datetime
x=str2num(strrep(a,':',''))
y=str2num(strrep(b,':',''))
then fine the difference between 2 dates
e = etime(x,y)
this will give you number of seconds between both times
Is there a method in matlab to convert seconds from a known date to a standard date time format?
For example, if I have a vector of values shown as seconds from 1901/01/01, how would I convert them to a dateTime? In this case a value of 28125 would correspond to 1981/01/01. Is there an efficient method for doing this?
The numbers in your example do not make sense so it is not clear if your time is in seconds or days but since you asked for seconds I will use this.
What you want to achieve can be done using datenum function. This function returns the number of (fractional) days from 1/1/0000. So first you need to find your offset, e.g.:
offsetInDays = datenum(1901,1,1);
Next, you convert the date from seconds to days:
dateInDays = YourRequiredDateInSec * 3600 * 24;
Finally, you date is given by
RequiredDate = datestr(offsetInDays + dateInDays);
I have some time as string format in my data. Can anyone help me to convert this date to milliseconds in Matlab.
This is an example how date looks like '00:26:16:926', So, that is 0 hours 26 minutes 16 seconds and 926 milliseconds. After converting this time, I need to get only milliseconds such as 1576926 milliseconds for the time that I gave above. Thank you in advance.
Why don't you try using datevec instead? datevec is designed to take in various time and date strings and it parses the string and spits out useful information for you. There's no need to use regexp or split up your string in any way. Here's a quick example:
[~,~,~,hours,minutes,seconds] = datevec('00:26:16:926', 'HH:MM:SS:FFF');
out = 1000*(3600*hours + 60*minutes + seconds);
out =
1576926
In this format, the output of datevec will be a 6 element vector which outputs the year, month, day, hours, minutes and seconds respectively. The millisecond resolution will be added on to the sixth element of datevec's output, so all you have to do is convert the fourth to sixth elements into milliseconds and add them all up, which is what is done above. If you don't specify the actual day, it just defaults to January 1st of the current year... but we're not using the date anyway... we just want the time!
The beauty with datevec is that it can accept multiple strings so you're not just limited to a single input. Simply put all of your strings into a single cell array, then use datevec in the following way:
times = {'00:26:16:926','00:27:16:926', '00:28:16:926'};
[~,~,~,hours,minutes,seconds] = datevec(times, 'HH:MM:SS:FFF');
out = 1000*(3600*hours + 60*minutes + seconds);
out =
1576926
1636926
1696926
One solution could be:
timeString = '00:26:16:926';
cellfun(#(x)str2num(x),regexp(timeString,':','split'))*[3600000;60000;1000;1]
Result:
1576926
Assuming that your date string comes in that format consistently, you could use something as simple as this:
test = '00:26:16:926';
H = str2num(test(1:2)); % hours
M = str2num(test(4:5)); % minutes
S = str2num(test(7:8)); % seconds
MS = str2num(test(10:12)); % milliseconds
totalMS = MS + 1000*S + 1000*60*M + 1000*60*60*H;
Output:
1576926.00
you can convert a single string with a date or even a vector by using datevec for conversion and the dot product
a = ['00:26:16:926' ; '08:42:12:936']
datevec(a,'HH:MM:SS:FFF') * [0 0 0 3600e3 60e3 1e3]'
ans =
1576926
31332936
My time comes back from a database query as following:
kdbstrbegtime =
09:15:00
kdbstrendtime =
15:00:00
or rather this is what it looks like in the command window.
I want to create a matrix with the number of rows equal to the number of seconds between the two timestamps. Are there time funcitons that make this easily possible?
Use datenum to convert both timestamps into serial numbers, and then subtract them to get the amount of seconds:
secs = fix((datenum(kdbstrendtime) - datenum(kdbstrbegtime)) * 86400)
Since the serial number is measured in days, the result should be multiplied by 86400 ( the number of seconds in one day). Then you can create a matrix with the number of rows equal to secs, e.g:
A = zeros(secs, 1)
I chose the number of columns to be 1, but this can be modified, of course.
First you have to convert kdbstrendtime and kdbstrbegtime to char by datestr command, then:
time = datenum(kdbstrendtime )-datenum(kdbstrbegtime )
t = datestr(time,'HH:MM:SS')
I have a dataset for which I have extracted the date at which an event occurred. The date is in the format of MMDDYY although MatLab does not show leading zeros so often it's MDDYY.
Is there a method to find the mean or median (I could use either) date? median works fine when there is an odd number of days but for even numbers I believe it is averaging the two middle ones which doesn't produce sensible values. I've been trying to convert the dates to a MatLab format with regexp and put it back together but I haven't gotten it to work. Thanks
dates=[32381 41081 40581 32381 32981 41081 40981 40581];
You can use datenum to convert dates to a serial date number (1 at 01/01/0000, 2 at 02/01/0000, 367 at 01/01/0001, etc.):
strDate='27112011';
numDate = datenum(strDate,'ddmmyyyy')
Any arithmetic operation can then be performed on these date numbers, like taking a mean or median:
mean(numDates)
median(numDates)
The only problem here, is that you don't have your dates in a string type, but as numbers. Luckily datenum also accepts numeric input, but you'll have to give the day, month and year separated in a vector:
numDate = datenum([year month day])
or as rows in a matrix if you have multiple timestamps.
So for your specified example data:
dates=[32381 41081 40581 32381 32981 41081 40981 40581];
years = mod(dates,100);
dates = (dates-years)./100;
days = mod(dates,100);
months = (dates-days)./100;
years = years + 1900; % set the years to the 20th century
numDates = datenum([years(:) months(:) days(:)]);
fprintf('The mean date is %s\n', datestr(mean(numDates)));
fprintf('The median date is %s\n', datestr(median(numDates)));
In this example I converted the resulting mean and median back to a readable date format using datestr, which takes the serial date number as input.
Try this:
dates=[32381 41081 40581 32381 32981 41081 40981 40581];
d=zeros(1,length(dates));
for i=1:length(dates)
d(i)=datenum(num2str(dates(i)),'ddmmyy');
end
m=mean(d);
m_str=datestr(m,'dd.mm.yy')
I hope this info to be useful, regards
Store the dates as YYMMDD, rather than as MMDDYY. This has the useful side effect that the numeric order of the dates is also the chronological order.
Here is the pseudo-code for a function that you could write.
foreach date:
year = date % 100
date = (date - year) / 100
day = date % 100
date = (date - day) / 100
month = date
newdate = year * 100 * 100 + month * 100 + day
end for
Once you have the dates in YYMMDD format, then find the median (numerically), and this is also the median chronologically.
You see above how to present dates as numbers.
I will add no your issue of finding median of the list. The default matlab median function will average the two middle values when there are an even number of values.
But you can do it yourself! Try this:
dates; % is your array of dates in numeric form
sdates = sort(dates);
mediandate = sdates(round((length(sdates)+1)/2));