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

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Sim on 20 Oct 2022
Commented: Sim on 21 Oct 2022
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
{} {0×0 double} {} {} {0×0 double} {} {} {0×0 double} {}
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 on 21 Oct 2022
thanks a lot @Voss! :-)

Voss on 20 Oct 2022
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]}