Creating dates tables with loop
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Juan Manuel Romero
on 12 Jul 2019
Commented: Juan Manuel Romero
on 15 Jul 2019
I am trying to build a matrix that contains dates separated by a time step. It woks well for the first two lines, but then it is missing a second. This is the answer i get
['16.04.2014 00:00:00'
'16.04.2014 01:00:00'
'16.04.2014 01:59:59'
'16.04.2014 02:59:59'
'16.04.2014 03:59:59'
'16.04.2014 04:59:59'
...]
It is happening only when I defined the time step as 1. Does anyone knos how can I make it work correctly?
dates(1,1)=datenum('16.04.2014 00:00:00', 'dd.mm.yyyy HH:MM:SS');
df=datenum('07.06.2016 23:59:59', 'dd.mm.yyyy HH:MM:SS'); %Final date
ddate=1; %specify time step in hours
for i=2:(df-dates(1))*24/ddate+1
dates(i,1)=dates(i-1,1)+(ddate/24);
end
%dates(end,2)=df;
dates=datetime(dates,'ConvertFrom','datenum', 'Format', 'dd.MM.yyyy HH:mm:ss');
2 Comments
dpb
on 12 Jul 2019
Edited: dpb
on 12 Jul 2019
for i=2:(df-dates(1))*24/ddate+1
dates(i,1)=dates(i-1,1)+(ddate/24);
end
You're introduced floating point rounding error by the division in a couble and the loop. "Don't do that!"
Also you're using the deprecated datenum to generate datetime -- don't do that, either! Just use datetime from the git-go...
But, your biggest problem is that you have shortened the time span by that second you lost by setting start at 00:00:00 of one day but ending at 23:59:59 of another day but making that time difference the differential instead of incrementing by an even hour.
You can't have 23:59:59 as your end value unless you have a 59 minute, 59 second hour at the end instead of a full hour or your average day is short by the one second spread over the number of hours from beginning to end.
Accepted Answer
Andrei Bobrov
on 15 Jul 2019
dates = (datetime(2014,4,16,0,0,0):hours(1):datetime(2016,6,8,0,0,0))';
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