MATLAB: Extracting field values from cell array of structures

cell arraysparforstructures

I have a cell array of structures. Each structure has the fields : Start, End, Id..
RP_Cell{1,1}.Start = [1 2 3; 4 6 4] 
RP_Cell{1,1}.End= [11 7 33; 4 16 9] 
RP_Cell{1,1}.Id= [23;-4] 
RP_Cell{1,2}.Start = [1 -2 4] 
RP_Cell{1,2}.End= [17 6 3] 
RP_Cell{1,2}.Id= [5] 
.
.
RP_Cell{2,1}.Start = [1 2 87; 4 23 1; 7 3 1] 
RP_Cell{2,1}.End= [15 65 21; 35 1 6; 6 3 1] 
RP_Cell{2,1}.Id= [9; 34; 56] 
.
.
.
.
Now, I want to have the data in the fields separately – Start_List, End_List
Start_List{1,1} = [1 2 3; 4 6 4] 
Start_List{1,2} = [1 -2 4]
.
.
Start_List{2,1} = [1 2 87; 4 23 1; 7 3 1]
. 
End_List{1,1} = [11 7 33; 4 16 9] 
End_List{1,2} = [17 6 3] 
.
.
End_List{2,1} = [15 65 21; 35 1 6; 6 3 1] 
.
How do I do this in the simplest way without using loops

Best Answer

Assuming that all cells of the RP_Cell cell array only contain a scalar structure with the same fields in the same order, you can transform the cell array into a structure array:
RP_Array = cell2mat(RP_Cell);
It is then trivial to transform that structure array into a cell array with struct2cell.
fnames = fieldnames(RP_Array);
Allfields = struct2cell(RP_Array);  %Creates a numfield x M x N cell array
%Allfields(1, :, :) corresponds to RP_Array(:, :).(fnames{1})
%Allfields(2, :, :) corresponds to RP_Array(:, :).(fnames{2})
%etc.
Start_List = squeeze(Allfields(strcmp('Start', fieldnames(RP_Array)), :, :));
End_List = squeeze(Allfields(strcmp('End', fieldnames(RP_Array)), :, :));
Note that if you know for sure that Start is the first field of the structure, you can dispense with the strcmp and simply use:
Start_List = squeeze(Allfields(1, :, :));
Using strcmp is safer, since if the order ever happen to change, it will find the correct field.
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