how can I find a specific data in time table in matlab?

I am trying to extract the freez-thaw cycles in a timetable.freezing of stone only occur when the temperature drops below−3 °C in a day and thawing when temperature rises above 1 °C in next day. My quastion is that how can I define a function for it and then retime the time table based on it.

I need to find the days with mean temperature below−3 °C, followed by a day with mean temperature above 1 °C.(meteorological data file in attachment.)

Answer 1

[Andrei Bobrov]

i = diff(3*(data_mean_daily.tabrizmat7 < -3) + (data_mean_daily.tabrizmat7 > 1)) == -2;
T_out = data_mean_daily([i;false]|[false;i],:);

as at Sebastian:

i = (data_mean_daily.tabrizmat7(1:end-1) < -3) & (data_mean_daily.tabrizmat7(2:end) > 1);
T_out = data_mean_daily(find(i(:)')+[0;1],:);

[Hamed Hedayatnia]

Thanks but the second part of my question: this day must follow by a day with temp>4

[Hamed Hedayatnia]

why did you put ==-2 in first line?

[Andrei Bobrov]

1 - 3 = -2     :)

k = 3*(data_mean_daily.tabrizmat7 < -3) + (data_mean_daily.tabrizmat7 > 1);
% in k: 3 - days with  temp < -3, 1 - days with temp > 1 degree
i = diff(k) == -2; % our days (1 - 3 = -2) 
T_out = data_mean_daily([i;false]|[false;i],:);

[Hamed Hedayatnia]

dear Andrei thanks for your answers,

difference between -3 and +1 is 4. should I put 4 instead of 2?

[Andrei Bobrov]

T_out in my comment gives the correct result?

I gave a solution for "I need to find the days with mean temperature below−3 °C, followed by a day with mean temperature above 1 °C."

[Hamed Hedayatnia]

Dear Andrei.

Yes,it give the correct answer but in result both of ddays are appeared.i.e: if 18th january temp increrase to above +1 and the day before is -3, in result(which the number of days are important) both of them are appeared. So we can see coupled days for each result. another question(since I wanna learn for my next tries): why did you multiply first value by 3(*3)?

[Hamed Hedayatnia]

one more q: how can I compare the day with the day before?

[Andrei Bobrov]

k = 3*(data_mean_daily.tabrizmat7 < -3) + (data_mean_daily.tabrizmat7 > 1);

k is the vector of days, if the element has a value of 3, then the temperature of this day is less than -3, if the value is 1, the temperature is more than +1. We are looking for a combination in our case [3; 1] or diff([3;1]).

Answer 2

[Sebastian Bomberg]

You can offset temperature by one day and compare against >= 4.

idx = data_mean_daily.tabrizmat7(1:end-1) >= 2 & ...    % temp at current day greater 2 AND
    data_mean_daily.tabrizmat7(2:end) >= 4;             % temp at next day greate 4

data_mean_daily(idx,:)

idx has one row less than data_mean_daily but the missing last row will be treated as false anyway.

[Andrei Bobrov]

+1