Read images based on datetime

I have +1000 images (in 'Struct') and would only like to use 'imread' on the images that equal the datetime in 'week1'.

How can I use a for loop (or other option) that only read the images during these certain times?

Thanks a lot for your suggestions

Answer 1

[Mathieu NOE]

hello Sigmund

this is a starter ....

In the middle of my brainstorming I was momentary worried that in 'Struct' the filename and date field seemed not to be consistent

like the first value are :

Timex(1).name = 'T_1_202110010600.jpeg' (and we could interpret that as 01 oct 2021 , 06:00 AM)

but date field gives :

Timex(1).date = '01-Oct-2021 08:14:06'

so after a few seconds of doubt I continued my work assuming that date field is correct and I should not take into account what Timex.name could suggest

Back to the code :

seems that both mat files will give two datenum arrays that do not really match 100% so there is a certain time gap between the two (if plot both you will see it)

now what i wanted to do is :

• find the nearest element in Struct for each element in Week
• remove the elements that are two far apart in terms of time laps ; NB the minimal time delta found here is 52 seconds , so up to you to decide the time tolerance

here I opted to keep only what is below 60 seconds of difference

you simply have to add your own code after imread ;

% load data
 load('Week1.mat')  
 load('Struct.mat')  
 
dd = datenum(start); % datetime data from file 'Week1.mat'
tt = [Timex.datenum]; % datetime data from file 'Struct.mat'

for ci = 1:numel(dd)
    [v(ci),struct_idx(ci)] = min(abs(dd(ci) - tt));
    delta_seconds(ci) = v(ci) * 24 * 60 * 60; % time delta between nearest datetime in 'Struct.mat' for a given datetime in 'Week1.mat'
end

% plot(delta_seconds)
min(delta_seconds)

% keep only files index for time delta below a certain threshold (in seconds)
week_ix = find(delta_seconds<=60);
struct_idx = struct_idx(week_ix);


% create list of files to read in 'Struct'
for ck = 1:numel(struct_idx)
    
    ind = struct_idx(ck);
    folder = Timex(ind).folder;
    filename = Timex(ind).name;
    Fdate = Timex(ind).date;
    F = fullfile(folder,filename);
    
    % your own code here 
    A = imread(F);
    
end
    

[Mathieu NOE]

hello

Problem solved ?

[Siegmund]

Hey Mathieu, thanks a lot for your input and apologies for the late reply.

You almost did too much work (but I should've made it clearer in my initial question).

The datetime in 'Week1' (written as yyyy-mm-dd HH:MM:SS) is normally always equal to the datetime in 'Struct' (written as T_1_yyyymmddHHMM).

So normally if I can find the datetime of Week1 in Struct, and then read those images that are equal.

I was trying to use 'find' in a loop but that seems a bit complicated as well.

Thanks again for your help.