How can i make a dinamic row in a matrix or a cell?

I have a slight problem concatenating a row from a certain array let's say:

%Normal Array

arr = [1,2,3;4,5,6];

%i want to encrease one row specific like this:

arr(1,:) = [arr(1,:), 7];

%I want this result:

arr => [1,2,3,7;4,5,6];

% but i still have this kind of error: "Error Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 1-by-2."

% ¿how can i solve this please? I also tried with cells but i have the same error:

c = {1,2,3};

c = {c;{3,2,4,5}};

c(1,:) = {c,{4}};

Thank in advance.

Answer 1

[the cyclist]

In MATLAB, there cannot be an "empty" spot in a numerical array. So, you need to decide what you want in that spot. Sometimes a zero or a NaN can be a placeholder. So, you could do

arr = [1,2,3;4,5,6];
arr = [arr [7;NaN]]

arr = 2×4

1 2 3 7 4 5 6 NaN

Similarly, a cell array could have an empty array in one location

C = num2cell([1,2,3;4,5,6])

C = 2×3 cell array
    {[1]}    {[2]}    {[3]}
    {[4]}    {[5]}    {[6]}

C = [C,{7;[]}]

C = 2×4 cell array
    {[1]}    {[2]}    {[3]}    {[       7]}
    {[4]}    {[5]}    {[6]}    {0×0 double}

[Cholo Aranda]

Thanks for your answer, if i want to added only to a specific row:

arr = [1,2,3;4,5,6;7,8,9];

It should be like this?:

arr(2,:) = [arr(2,:),[77;NaN;NaN]];

Or how can i manage only a specific row.

Thanks you in advance.

[the cyclist]

You need to think of this as adding a complete column. So, your syntax does not work, because it is trying to append "column" of three more elements only to the second row, which does not make sense.

The following will work to add one element to the second row, but leaving the other rows "empty":

arr = [1,2,3;4,5,6;7,8,9];
arr = [arr,[NaN; 77; NaN]]

arr = 3×4

1 2 3 NaN 4 5 6 77 7 8 9 NaN

[Cholo Aranda]

thank you very much :)