# Add new "datetime" elements to an existing cell array (matrix)

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Sim on 24 Oct 2022
Commented: Star Strider on 24 Oct 2022
What I have so far:
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))
idx = 3×1
1 2 9
a(idx) = num2cell(b)
a = 3×3 cell array
{[24-Oct-2022 00:01:35]} {0×0 double} {0×0 double } {[24-Oct-2022 00:01:11]} {0×0 double} {0×0 double } {0×0 double } {0×0 double} {[24-Oct-2022 00:04:21]}
What I need / Desired output: add further elements to the cell array (matrix) "a".
% For example, add the new element "datetime({'00:01:01'})"
% to the cell "index = [3 3]", i.e. "idx = 9":
a =
3×3 cell array
{[24-Oct-2022 00:01:35]} {0×0 double} {0×0 double }
{[24-Oct-2022 00:01:11]} {0×0 double} {0×0 double }
{0×0 double } {0×0 double} {[24-Oct-2022 00:04:21], [24-Oct-2022 00:01:01]}
My attempt:
new_element = datetime({'00:01:01'});
a(9) = a + num2cell(new_element)
Operator '+' is not supported for operands of type 'cell'.

Star Strider on 24 Oct 2022
I am not certain what a more universal end result would look liks, however this seems to work for this problem —
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))
idx = 3×1
1 2 9
a(idx) = num2cell(b)
a = 3×3 cell array
{[24-Oct-2022 00:01:35]} {0×0 double} {0×0 double } {[24-Oct-2022 00:01:11]} {0×0 double} {0×0 double } {0×0 double } {0×0 double} {[24-Oct-2022 00:04:21]}
new_element = datetime({'00:01:01'})
new_element = datetime
24-Oct-2022 00:01:01
a{9} = [a{9} new_element] % Concatenate
a = 3×3 cell array
{[24-Oct-2022 00:01:35]} {0×0 double} {0×0 double } {[24-Oct-2022 00:01:11]} {0×0 double} {0×0 double } {0×0 double } {0×0 double} {[24-Oct-2022 00:04:21 24-Oct-2022 00:01:01]}
The operation is a simple concatenation, using the [] concatenation operators.
.
Star Strider on 24 Oct 2022
As always, my pleasure!