Return character array with increasing size based on input

I'm trying to make a cell-array that increases in length and has the previous characters in the following cells + the next letter in the alphabet

the inputs are supposed to be a starting letter and a number that indicates the amounts of cells(and then also the amount of letters in the last cell)

k = input('write startingletter and then number:')
k = a3
g = str2num(k(2:end))
inncell{1,1} = k(1);
inncell{1,2} = g;
outcell = makecell(inncell) %the function makecell
outcell=
    {'a'}    {'ab'}    {'abc'}...
        

this is the output I need

and this is what I've come up with, but it's not working

% a = 97, z = 122 ASCII
k = input('gimme one letter then one pos. number(exs: a5):','s');
g = str2num(k(2:end));

while isletter(k(1))~= 1 || isempty(g) || g <= 0
    %errorcheck if invalid input
    disp('----ERROR! input ONE letter THEN ONE POSITIVE number');
    k = input('gimme one letter then one pos. number(exs: a5):','s');
    g = str2num(k(2:end));
end

inncell{1,1} = k(1);
inncell{1,2} = g;
outcell = makecell(inncell);

function outcell = makecell(inncell)
n = inncell{2};
outcell = cell(1,n);
for i = 1:n
    for k = 1:i
        if k == 1
            outcell{1, i} = char(double(inncell{1}));
        else
            outcell{1, i} = strcat(char(double(inncell{1}), char(double(inncell{1})+ k-1)));
        end
        
    end
end
end

[Walter Roberson]

There is a one line solution once you know the starting letter and length ;-)

[Nikolai]

yeah, I gotta look into matlab functions more, I'm still very new to the whole programming thing, so I'll keep working hard at it!

(would have been nice with a pointer to which funtion you mean though :P )

[Walter Roberson]

It is not one function, it is a single expression.

Hint:

10 11 12 13 14
10 11 12 13 14
10 11 12 13 14
10 11 12 13 14
10 11 12 13 14

-->

10  0  0  0  0
10 11  0  0  0
10 11 12  0  0
10 11 12 13  0
10 11 12 13 14

looks like a triangle of entries.

Answer 1

[dpb]

strt=input('Starting letter: ');
N=input('Number groups: ');
% do your error checking here to ensure a single starting character and integer length in reason
...
res=cell(1,N);             % preallocate the cell array
res(1)=cellstr(strt);      % initial single letter
for i=2:N
  res(i)=cellstr(strt:char(strt+i-1));
end

"Brute force, deadahead!" solution of creating each substring independently rather than trying to catenate onto an existing cell...does take advantage of Matlab's ability to do arithmetic on char() arrays/variables that makes things easier to code.

Example:

>> strt='a';
>> N=4;
>> res=cell(1,N);
>> res(1)={strt};
>> for i=2:N,res(i)={strt:char(strt+i-1)};end
>> res
res =
  1×4 cell array
    {'a'}    {'ab'}    {'abc'}    {'abcd'}
>> 

[Nikolai]

thank you so very much

I didn't realize you could use the colon operator that way with letters, but it meakes sense for me now. I've been walking around in circes for a couple of hour trying to figure it out, (got a bad habit of not using Matlab functions when it really does make life easier, thank you so very much!

[dpb]

"...could use the colon operator that way with letters"

Yes, a char() array is just an array of characters; they're just integers internally that the display system knows to map to the right displayable characters. But, they can be treated like numbers when convenient, such as here...just have to cast back to the char() type because

>> 'a'+0
ans =
    97
>> 

changes the type to double...