MATLAB: Input data from one array to another

cell arraysdatadata import

Hello. I'm currently trying to implement data from a dataset to a variable, as a function of time. I've tried the answers which are already here, but have been unsuccesful.
Current script:
time=365;       % [days] Calculation time
dt=0.1;         % [days] Timestep
nt=time/dt;     % [-]    Calculation steps
tempdata is a [365,2] dataset with an index in column 1 and temperature data in column 2.
for i=2:nt
   for j=1:365
      T(1)=tempdata(1,2);     % Starting condition for T, as i=2:nt
      Dt(1)=0;                % Time elapsed
      Dt(i)=Dt(i-1)+dt;
        % I want to set up an if function, which takes the temperature data
        % from tempdata(j,2) and puts it into T(i), if Dt(i) is equal to
        % tempdata(j,1).
        if Dt(i)==tempdata(j,1);
           T(i)=tempdata(j,2);
        else
           T(i)=T(i-1);
        end
     end
  end
This function however doesn't work. I firstly don't understand why, and secondly don't know any other way of doing this. Any of you guys know how?
Much appreciated 🙂

Best Answer

The main problem with your code was the double for loop. Even if a match was found, for say j=50; it was overwritten in the second iteration with j=51 and T(i)=T(i-1); Here is a code that should do what you want:
time=365;       % [days] Calculation time
dt=0.1;         % [days] Timestep
nt=time/dt;     % [-]    Calculation steps
Dt=0:dt:365;  %So a vector from 0 to 365 in steps of 0.1
T=Dt*NaN;  %Define a vector of the same length as Dt, start with NaN's everywhere
T(1)=tempdata(1,2); %First element fixed
for j=1:365 %Put all the exact matches
        T(Dt==tempdata(j,1))=tempdata(j,2);
end
for j=2:length(T) %If no match found, put equal to previous element
      if isnan(T(j))
          T(j)=T(j-1);
      end;
end
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