Better way to pull out values from a struct

I have a matrix with a matrix CT of struct data called callsTable. I'm trying to pull out just one of the columns called Time and create a 1D vector using the following code. Is there a better way that I can do this? Currently, running the code I get the following error message.

Unable to perform assignment because the size of the left side is 28-by-1 and the size of the right side is

6-by-1.

for k=1:size(CT,1)
    for i=size(CT(k),1)
        
         T(:,i)=CT(k).callsTable.Time
      
    end
end

Answer 1

[Walter Roberson]

Times = arrayfun(@(S) S.callsTable.Time, CT, 'uniform', 0);

T = horzcat(Times{:});

The assignment to T will fail if the Time vectors were not all the same size.

Answer 2

[Sam Litvin]

Thanks Walter

I tried that, got this: Error using horzcat, Dimensions of arrays being concatenated are not consistent.

So then I tried vertcat instead, but got same issue as before. I am preallocatin the matrix by scanning the CT to find the max number there and creating a matrix of zeros

for n=1:size(CT,1)
    
    call_tot=size(CT(n).callsTable.Time);
    calls(n,:)=call_tot;
    
end
        tablsize=size(CT,1); 
        maxcalls=max(calls);
        T=zeros(maxcalls(1),tablsize);

[Walter Roberson]

time_lengths = arrayfun(@(S) length(S.callsTable.Time), CT);
max_time_lengths = max(time_lengths);

FirstN = @(V, N) V(1:N);
PadN = @(V, N) FirstN([V; zeros(N,1)]);
Times = arrayfun(@(S) PadN(S.callsTable.Time, max_time_lengths), CT, 'uniform', 0);
T = horzcat(Times{:});

[Walter Roberson]

time_lengths = arrayfun(@(S) length(S.callsTable.Time), CT);
max_time_lengths = max(time_lengths);
FirstN = @(V, N) V(1:N);
PadN = @(V, N) FirstN([V; zeros(N,1)], N);
Times = arrayfun(@(S) PadN(S.callsTable.Time, max_time_lengths), CT, 'uniform', 0);
T = horzcat(Times{:});

Answer 3

[Sam Litvin]

Thanks Walter, I really appreciate it.

Interesting method, I like it. Could you please explain what you're doing here:

FirstN = @(V, N) V(1:N);
PadN = @(V, N) FirstN([V; zeros(N,1)]);

because I get this error and I'm not sure how to debug

Not enough input arguments.

Error in Euler_GLM>@(V,N)V(1:N) (line 20)
FirstN = @(V, N) V(1:N)

Error in Euler_GLM>@(V,N)FirstN([V;zeros(N,1)]) (line 21)
PadN = @(V, N) FirstN([V; zeros(N,1)]);

Error in Euler_GLM>@(S)PadN(S.callsTable.Time,max_time_lengths) (line 22)
Times = arrayfun(@(S) PadN(S.callsTable.Time, max_time_lengths), CT, 'uniform', 0);

[Walter Roberson]

FirstN: takes the first N elements of whatever is handed in

PadN : take whatever input is given and always add N zeros at the end of it, and then call FirstN to pull out the first N of whatever that ends up being

So for example, PadN([1;2;3], 7) would form [1;2;3;0;0;0;0;0;0;0] and then ask FirstN to take the first 7 of those, getting out [1;2;3;0;0;0;0] as the result.

There are other ways of constructing something like this, including

PadN = @(V, N) [V; zeros(N-length(V), 1)]

which does not require as many steps.