Creating an array of datenum(s)

I'm new to datenum, datestr etc and I have a relatively simple question:

I know the original start date of my monthly data:

>> datenum([1871 1 15 0 0 0])

ans =

      683384

and that I have 141 months total. How do I populate an array so that I can match it to another time vector that I've already created? (see below)

Essentially I'm looking for:

time_index=ismember(first_tv,second_tv);

>> tv

tv =

          1999           3          15           0           0           0
          1999           4          15           0           0           0
          1999           5          15           0           0           0
          1999           6          15           0           0           0
          1999           7          15           0           0           0
          1999           8          15           0           0           0
          1999           9          15           0           0           0
          1999          10          15           0           0           0
          1999          11          15           0           0           0
          1999          12          15           0           0           0
          2000           1          15           0           0           0
          2000           2          15           0           0           0
          2000           3          15           0           0           0
          2000           4          15           0           0           0
          2000           5          15           0           0           0
          2000           6          15           0           0           0
          2000           7          15           0           0           0
          2000           8          15           0           0           0
          2000           9          15           0           0           0
          2000          10          15           0           0           0
          2000          11          15           0           0           0
          2000          12          15           0           0           0
          2001           1          15           0           0           0
          2001           2          15           0           0           0
          2001           3          15           0           0           0
          2001           4          15           0           0           0
          2001           5          15           0           0           0
          2001           6          15           0           0           0
          2001           7          15           0           0           0
          2001           8          15           0           0           0
          2001           9          15           0           0           0
          2001          10          15           0           0           0
          2001          11          15           0           0           0
          2001          12          15           0           0           0
          2002           1          15           0           0           0
          2002           2          15           0           0           0
          2002           3          15           0           0           0
          2002           4          15           0           0           0
          2002           5          15           0           0           0
          2002           6          15           0           0           0
          2002           7          15           0           0           0
          2002           8          15           0           0           0
          2002           9          15           0           0           0
          2002          10          15           0           0           0
          2002          11          15           0           0           0
          2002          12          15           0           0           0
          2003           1          15           0           0           0
          2003           2          15           0           0           0
          2003           3          15           0           0           0
          2003           4          15           0           0           0
          2003           5          15           0           0           0
          2003           6          15           0           0           0
          2003           7          15           0           0           0
          2003           8          15           0           0           0

%and have turned my time vector into a datenum:

second_tv =

        730194
        730225
        730255
        730286
        730316
        730347
        730378
        730408
        730439
        730469
        730500
        730531
        730560
        730591
        730621
        730652
        730682
        730713
        730744
        730774
        730805
        730835
        730866
        730897
        730925
        730956
        730986
        731017
        731047
        731078
        731109
        731139
        731170
        731200
        731231
        731262
        731290
        731321
        731351
        731382
        731412
        731443
        731474
        731504
        731535
        731565
        731596
        731627
        731655
        731686
        731716
        731747
        731777
        731808

Thanks!

[Cedric]

What is the purpose ultimately? What do you want to do with the match?

[Kate]

Cedric, what I'm looking to do it pull (in this case reanalysis meteorological drivers which span 140 yrs) which match the time period for my flux data (which varies by site, but in this example lasts ~5 years (give or take a few months on either end)).

Essentially I'm trying to get to:

time_index=ismember(met_tv,flux_tv);

%pull grid location of fluxnet data
[i,j]=findGridcell(site, .5); %this works fine

metdriver=metdriver(i, j, time_index); %this is what I'm stuck on b/c of time vector issues

sensitivity=flux_data/metdriver; %end-product that I need

Does that make sense?

Answer 1

[Kate]

FYI/for future reference:

>> ((datenum([repmat(1871,1692,1) [1:1692]' repmat([15 0 0 0],1692,1)])));

Answer 2

[Matt Kindig]

If I understand you correctly, this should do it:

[~, time_index] = ismember( datenum(tv), second_tv);

[Kate]

So I actually don't have my first tv yet, I need to create it. It's a monthly value that starts in 1871 and goes to present. Once I create it I can find matches between my first tv and my second tv. Does that make sense?

Answer 3

[J.C.]

Why not just use a loop?

t(1:141, 1) = zeros;
t(1) = datenum([1871 1 15 0 0 0]);

for i = 2:141
    t(i) = addtodate(t(i-1), 1, 'month');
end

[Kate]

You're right JC, I was making this too complicated. I ended up doing:

>> ((datenum([repmat(1871,1692,1) [1:1692]' repmat([15 0 0 0],1692,1)])));

Which does the same thing without a loop.