Reading in data and plotting the sunrise/sunset time of different dates against the time.

Question

Mamed 2012-1-12

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回答： Peter Perkins 2018-2-6

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Hi

I was wondering if there is a way to plot the sunset time against the date of a month.

I have data that i can get from http://www.stjarnhimlen.se/2011/stockholm.html.

The data for January looks like Translation

 Date   Dusk   Up    ??     ??     Down  Dawn   | Same but for the moon.
Datum                    Solen                             Månen
        Gry    Upp   I mer  Dekl   Ned   Skym    Upp   I mer  Dekl   Ned   *-tid
 1 Lö   6:29   8:44  11:51 -23,0  14:59  17:13   6:11   9:10 -23,4  12:06   6:41
 2 Sö   6:29   8:44  11:52 -22,9  15:00  17:14   7:20  10:07 -24,2  12:54   6:45
...

Sorry the site is in Swedish, but data I'm interested in is 'Upp'(Up) and 'Ned' (Down) for 'Solen' (Sun).

So I wanna import this and plot the date against the time

plot(date,time)

but when i try to import it the time creates vectors because of the ' : ' and it also complains of the non strings for the days and non english letters.

I did cleaning manually and got this

aa = [
   1   8 44  14 59 
   2   8 44  15 00 
...
]

So now we have 'Date' 'hh' 'mm' 'hh' 'mm'. and i thought of maybe using

datenum('aa(:,2):aa(:,3)','HH:MM')

but it doesnt take vector and i have no idea how to plot so it says the time hh:mm in the y axis.

Any ideas?? Thanks

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Answer 1

David 2012-1-12

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This should work

datenum([num2str(aa(:,2)) repmat(':',size(aa(:,2))) num2str(aa(:,3))],'HH:MM')

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Answer 2

Mamed 2012-1-12

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Hi, that work fine to make read the time, but when i plot i wanna have the axis to read HH:MM (ie 07.00) now it is in the scale 7.3487e5.

up = datenum([num2str(aa(:,2)) repmat(':',size(aa(:,2))) num2str(aa(:,3))],'HH:MM');
do = datenum([num2str(aa(:,4)) repmat(':',size(aa(:,4))) num2str(aa(:,5))],'HH:MM');
plot(aa(:,1),up);

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Answer 3

David 2012-1-12

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Look at

datetick(tickaxis)

this will reformat your datenum into which every date format you like on your axis

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Answer 4

Peter Perkins 2018-2-6

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As Jan points out, the real question here was the plotting. Since this was originally answered six years ago, in versions of MATLAB beginning in R2014b, plotting times and dates became much easier:

Scraping web pages isn't my forte, so I copied the data to a text file, removed blank lines, removed embedded blanks in "-- --", and added column heading for the day-of-month and weekday columns. Given that:

t = readtable('tmp1.txt','HeaderLines',1);
up = timeofday(datetime(t.Upp,'Format','HH:mm')); % convert text -> datetime -> duration
down = timeofday(datetime(t.Ned,'Format','HH:mm'));
date = datetime(2018,1,t.i);
plot(date,up,'bo',date,down,'rx')