CODEWITHSUNDEEP
matlabdate
user3876557
user3876557

Reputation: 47

Changing seconds in the date vector

I would like to keep the seconds uniform in my time vector using Matlab.

for example in my data the time vector is

01-01-2007 14:18:30; 01-01-2007 14:19:30;01-01-2007 14:20:38;01-01-2007 14:21:28

and so on.. I want it to keep it uniform to 

01-01-2007 14:18:30; 01-01-2007 14:19:30;01-01-2007 14:20:30;01-01-2007 14:21:30.

Any help would be greatly appreciated Thanks. S.S

Upvotes: 0

Views: 43

Answers (2)

Dan
Dan

Reputation: 45752

So it depends on how your dates are stored

As a string array:

s = ['01-01-2007 14:18:30'; 
     '01-01-2007 14:19:30';
     '01-01-2007 14:20:38';
     '01-01-2007 14:21:28']

s(:,end-1:end)= repmat('30', size(s,1),1)

or if for some reason you don't want to use repmat (this might be faster), you can take advantage of the fact that Matlab automatically broadcasts scalars:

s(:,end-1)='3';
s(:,end)= '0';

or as a cell array of strings:

c = {'01-01-2007 14:18:30'; 
     '01-01-2007 14:19:30';
     '01-01-2007 14:20:38';
     '01-01-2007 14:21:28'}

cellfun(@(x)([x(1:end-2),'30']), c, 'uni', false)

or if you have your dates as numbers then

s = ['01-01-2007 14:18:30'; 
     '01-01-2007 14:19:30';
     '01-01-2007 14:20:38';
     '01-01-2007 14:21:28']
n = datenum(s, 'dd-mm-yyyy HH:MM:SS')

%// Note that n will store numbers in units of days, so to round off to the nearest 30 seconds we must round to multiples of 1/(# of 30 seconds per day)
k = 2*60*24; %//The number of 30 seconds per day
round(n*k)/k

or with any of them, you can covert to a date vector:

v = datevec(s, 'dd-mm-yyyy HH:MM:SS')

or

v = datevec(n)

where s or n are defined as above. Now you can simply go

v(:,end) = 30;

and then use datestr(v) or datenum(v) to go back.

Upvotes: 1

EJG89
EJG89

Reputation: 1189

In the data strings the last the seconds are always the last two places in the string so you can just replace them by using:

date_string='01-01-2007 14:18:28';
uni_seconds = '30';

date_string(end-1:end)=uni_seconds

The last line states that the last two places (end-1 and end) are to be replaced by the variable uni_seconds which is the string containing the seconds you want to set.

Upvotes: 1

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