code vectorization: assign numbers or datetime/durations to cell arrays, without any loop

Here following I am trying to assign numbers or datetime/durations to a cell array, without any loop.

In one case the result is correct (as expected), in other two cases the results are not correct.

How to fix the cases that do not give the correct result ?

Case 1 : the result is correct

a = cell(3,3);
index = [1 1
         2 1];
a(index(:,1),index(:,2)) = {1}

a = 3×3 cell array
    {[       1]}    {0×0 double}    {0×0 double}
    {[       1]}    {0×0 double}    {0×0 double}
    {0×0 double}    {0×0 double}    {0×0 double}

Case 2 : the result is not correct

a = cell(3,3);
index = [1 1
         2 1
         3 3];
a(index(:,1),index(:,2)) = {1}

a = 3×3 cell array
    {[1]}    {0×0 double}    {[1]}
    {[1]}    {0×0 double}    {[1]}
    {[1]}    {0×0 double}    {[1]}

I woud have expected the following result, as the correct one:

    {[       1]}    {0×0 double}    {0×0 double}
    {[       1]}    {0×0 double}    {0×0 double}
    {0×0 double}    {0×0 double}    {[       1]}

Case 3 : the result is not correct

a = cell(3,3);
index = [1 1
         2 1
         3 3];
b = datetime({'00:01:35'
             '00:01:11'
             '00:04:21'});
a(index(:,1),index(:,2)) = {b}

a = 3×3 cell array
    {3×1 datetime}    {0×0 double}    {3×1 datetime}
    {3×1 datetime}    {0×0 double}    {3×1 datetime}
    {3×1 datetime}    {0×0 double}    {3×1 datetime}

I woud have expected the following result, as the correct one:

    {'00:01:35'}    {0×0 double}    {0×0 double}
    {'00:01:11'}    {0×0 double}    {0×0 double}
    {0×0 double}    {0×0 double}    {'00:04:21'}

[Sim]

thanks a lot @Voss! :-)

Answer 1

[Voss]

Use sub2ind.

Case 1:

a = cell(3,3);
index = [1 1
         2 1];

idx = sub2ind(size(a),index(:,1),index(:,2));

a(idx) = {1}

a = 3×3 cell array
    {[       1]}    {0×0 double}    {0×0 double}
    {[       1]}    {0×0 double}    {0×0 double}
    {0×0 double}    {0×0 double}    {0×0 double}

Case 2:

a = cell(3,3);
index = [1 1
         2 1
         3 3];

idx = sub2ind(size(a),index(:,1),index(:,2));

a(idx) = {1}

a = 3×3 cell array
    {[       1]}    {0×0 double}    {0×0 double}
    {[       1]}    {0×0 double}    {0×0 double}
    {0×0 double}    {0×0 double}    {[       1]}

Case 3:

a = cell(3,3);
index = [1 1
         2 1
         3 3];
b = datetime({'00:01:35'
             '00:01:11'
             '00:04:21'});

idx = sub2ind(size(a),index(:,1),index(:,2));

a(idx) = num2cell(b) % use num2cell to convert from datetime array to cell array

a = 3×3 cell array
    {[20-Oct-2022 00:01:35]}    {0×0 double}    {0×0 double            }
    {[20-Oct-2022 00:01:11]}    {0×0 double}    {0×0 double            }
    {0×0 double            }    {0×0 double}    {[20-Oct-2022 00:04:21]}