MATLAB: Struct to cell array

cell arraysMATLABstructures

I was working with structs and cell array and I came across something I didn't quite understand.

If I have a struct and its transpose –

s = struct('A',{1;2;3}) % 3x1 struct
sT = struct('A',{1,2,3}) % 1x3 struct

Then using dot notation to select a single field will produce a cell array with the same dimensions either way –

d = {s.A} % 1×3 cell

dT = {sT.A} % 1×3 cell

Why aren't d and dT transposes of each other?

Why? Because Matlab works that way.

>> nums.f
ans =
     1
ans =
     2
ans =
     3

outputs a list and

{}

concatenates the list horisontally into a cell array.

Your example concatenates horizontally because it is exactly equivalent to doing this:

[structure(1).field,structure(2).field]

which is just shorthand for

horzcat(structure(1).field,structure(2).field)

If you want to concatenate vertically, use either of these

vertcat(structure.field)
cat(1,structure.field)

For more information on how to use comma-separated lists:

Use getfield with a comma-separated list:

a.b.c.d = pi;
x = {'b','c','d'};
getfield(a,x{:})
ans = 3.1416