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Line comment change string cell shape

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JackXu
JackXu on 20 Dec 2019
Commented: JackXu on 20 Dec 2019
I found when I use line comment to erase some my content for a string cell, the cell shape change to row from original column
like this
>> a={'first' ...
, 'second' ...
, 'third'}
a =
'first' 'second' 'third'
>> a={'first' ...
% , 'second' ...
, 'third'}
a =
'first'
'third'
I have already tried 2013a and 2015b, they shared the same result.
I just want to change my test case sometime quickly for a simple test, but that messed up the following code with my for loop will use like this
for a_n = a
a_n = a_n{:};
That will be good if I don't comment anything, but failed to only loop once with my first case.
Any answer about why the shape of string cell will change when there are line comments is appreciated.
  2 Comments
JackXu
JackXu on 20 Dec 2019
Thanks a lot, you understood my question.
I really meant to ask that can I keep my matrix shape with this kind of matrix initalization.
I want to line up my operation case into every single line, so that I can just use line comment (ctrl + R) or line uncomment (ctrl + T) quickly to change my operation content and run another turn easily with F5.
I can't easily organize my initialization into just one line, because the string I use usually is about 8 in length, and I get 10 case string. If they are all into one line, that would be horrible to find and change anything like that.
Furthermore, I already find another bad news for this kind of writing method. If I don't comment second line but comment the third line, only error I can get. So comment different line also has different result?
>> a = {'first' ...
, 'second' ...
% , 'third' ...
, 'four' ...
}
Dimensions of matrices being concatenated are not consistent.
So, how this
...
works?
I only find this to tell me I just can use (...) for multi lines
https://ww2.mathworks.cn/help/matlab/matlab_prog/continue-long-statements-on-multiple-lines.html?lang=en
Now, it seems that line comment will change the effect of ellipsis. I want to know more about both of them, so I may find other way to change my code. Of course, if you could share your method to organize plenty of operation case, that would be really really helpful.
Always, thanks a lot for your help. And all help is appreciated.

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Accepted Answer

Chien-Han Su
Chien-Han Su on 20 Dec 2019
Edited: Chien-Han Su on 20 Dec 2019
I just try a two different line comment (matlab2019b), and here are the results,
(1)
>> a = {'A', 'B'}
a =
1×2 cell array
{'A'} {'B'}
(2)
>> a = {'A'
,'B'}
a =
2×1 cell array
{'A'}
{'B'}
You can see that matlab sees the second assignment equal to
a = {'A';'B'}
So a column cell array is assigned.
In your example,
a={'first' ...
% , 'second' ...
, 'third'}
equals to
a={'first' ... % , 'second' ...
, 'third'}
and
a={'first'
, 'third'}
Hence you get a column like the previous (2).
If you want to erase some content and keep the row shape at the same time, maybe you should also add '...' before the '%', namely,
a={'first' ...
... % , 'second' ...
, 'third'}
gives you
a =
1×2 cell array
{'first'} {'third'}
  3 Comments
JackXu
JackXu on 20 Dec 2019
Awesome! We made it in the same way.
I already changed my code like this
>> a = {'first' ...
; 'second' ...
% ; 'third' ...
; 'fourth' ...
};
a = reshape(a, 1, numel(a))
a =
'first' 'second' 'fourth'
And now it alrealy works fine and it is totally my style.
I barely use
a = a(:)
because I always misunderstand what this
(:)
will give me, and
reshape
is much clear. Also,
a'
is clear but context-sensitive, and I just use it when I need transpose.
It just like the symbol we use in linear algebra.
Always, you are great helpful!

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