Error using vertcat Dimensions of arrays being concatenated are not consistent.

This seems to be a trivial problem but I am struggling to figure it out. Why is it that when I define

some_var = ['AB'; 'CD'; 'EF'],

then there is no error, but when I write

some_var_full = ['alpha beta'; 'gamma eps'; delta phi'], it generates an error mesage:

Error using vertcat

Dimensions of arrays being concatenated are not consistent.

How can I fix it? Thank you so much in advance for helping me.

Answer 1

[Chunru]

% some_var = ['AB'; 'CD', 'EF']  
% semicolon for new rows and comma for new coloumn.  so the above is wrong

% The code below is OK (each row has same number of characters in order to
% form a 2d char array
some_var = ['AB'; 'CD'; 'EF']  

some_var = 3×2 char array
    'AB'
    'CD'
    'EF'

% some_var_full = ['alpha beta'; 'gamma eps'; 'delta phi']
% The above is wrong since the 1st line has more characters than other
% lines
% You can make each line has same number of characters
some_var_full = ['alpha beta'; 'gamma eps '; 'delta phi ']

some_var_full = 3×10 char array
    'alpha beta'
    'gamma eps '
    'delta phi '

% It is better to use string array
some_var_full = ["alpha beta"; "gamma eps"; "delta phi"]

some_var_full = 3×1 string array
    "alpha beta"
    "gamma eps"
    "delta phi"

[alphabetagamma]

I see. Thank you so much. This is a subtle difference to note.

Answer 2

[Walter Roberson]

'AB' is a 1 x 2 array of character

'CD' is a 1 x 2 array of character

['AB';'CD'] is asking to vertically concatenate a 1x2 and a 1x2. The number of columns match so the result is well defined to create 2x2 array of character

'alpha beta' is a 1x10 array of character

'gamma eps' is a 1x9 array of character.

When you [;] those together you are asking to vertically concatenate a 1x10 array and a 1x9 array. The number of columns do not match so it is an error.

You might want to switch to using

some_var_full = ["alpha beta"; "gamma eps"; "delta phi"]

Now each of the rows is a 1x1 string() object instead of being character vectors.

[alphabetagamma]

Very helpful. This clears up my confusion. Thanks :)