how can I insert comments into a multiline array creation?

This works

>> p = [...
%%%BEGIN ENTRIES %%%
     'a1;', ...
     'b;', ...
     'c;'
     ]

p =

a1;b;c;

but commenting out the 'b' line doesn't

p = [...
%%%BEGIN ENTRIES %%%
     'a1;', ...
     % 'b;', ...
     'c;'
     ]

    Dimensions of matrices being concatenated are not consistent.

Answer 1

[Walter Roberson]

p = [...
%%%BEGIN ENTRIES %%%
     'a1;', ...
     ... % 'b;', ...
     'c;'
     ]

Note: ... itself acts as a comment operator for the rest of the line, so you could get away with

p = [...
%%%BEGIN ENTRIES %%%
     'a1;', ...
     ... 'b;', ...
     'c;'
     ]

However this would tend to confuse people as it is not common to use this and readers might not pick up on the fact the rest of the line was a comment.

[Andrew Diamond]

Thanks so much. So, is the idea that like a % an continuation ellipses means "ignore the rest of the line"? But then why does that work and not %? Inquiring minds want to know.

[Walter Roberson]

... has the side effect of also ignoring the rest of the line, but it has the primary effect of continuing the previous statement.

The portion of the 'b;' line before the % is not commented out, so

p = ['a1;', ...
     % 'b;', ...
     'c;']

is the same as

p = ['a1;', ...

       'c;']

which is not the same as

 p = ['a1;', ...
       'c;']

The

    p = ['a1;', ...

       'c;']

version should be looked at as if it were

p = ['a1;', ...
     []
     'c;']

which would be the same as

 p = ['a1;', []
       'c;']

The default within [] is that lines that do not end in continuation are treated as if they had ; at the end of them, so this is

 p = ['a1;', [];
       'c;']

which is

 p = ['a1;';
       'c;']

and that fails because the number of columns is not equal.

Answer 2

[Andrew Diamond]

I've been doing matlab for about 30 years and I didn't know this (the implicit empty array row insertion as well as the continuing ellipses at the start of a line as a continuation of the previous line etc). You learn something new every day.

again, thanks so much.

[Fergil Mills]

^ Agree w Andrew, thanks so much for posting this answer!