How can I index-match in Matlab?

Hello there,

I have two time series. DryFlow includes date&time in column one and flow in column 2, i.e.:

736486.166666667	0.145156348804779
736486.170138889	0.150701650979673
736486.173611111	0.145156348804779
736486.180555556	0.0437043849475129
736486.190972222	0.143321742197341
736486.194444445	0.0281703489965504
736486.201388889	0.145156348804779
736486.211805556	0.155368503029057

Night_mins include an exact date in column 1 and flows in column 2:

736486	0.0281703489965504
736490	0.0920976912283344
736491	0.191993056344663
736492	0.159130595744160

What I wish to do is essentially index-match the data like in Excel - where DryFlow(:,1)==Night_min(:,1) create a vector so that the corresponding Night_min flow is listed for every point measured. For example:

Night_min includes the minimum flows measured each day - i.e. one value per day. DryFlow includes the flow measured at every point during the day, with multiple measurements for each day. I would like to subtract Night_min(:,2) from DryFlow(:,2) where these indexes (the day) match. How can we do this? I've tried a double-for loop, but I do not get the right answer (I checked this manually in excel). In this case, FS should be the vector of DryFlow(:,2)-Night_min(:,2).

for i=1:length(Night_min(:,1))
    for k=1:length(DryFlow(:,1))
        if Night_min(i,1)==floor(DryFlow(k,1))
            FS(k)=DryFlow(k)-Night_min(i);
        end
    end
end

Any help would be greatly appreciated!

Answer 1

[KL]

I woould actually create another column in DryFlow array to store the result.

change this to,

FS(k)=DryFlow(k)-Night_min(i);

to

DryFlow(k,3) = DryFlow(k,2) - Night_min(i,2);