Performing operation with loop index inside for-loop doesn't work as expected

Hi I'm trying to print an upside-down triangle of hash marks using a for loop. Here's what I've got so far:

 n=input('How many hashtags would you like to print today? : ');
 m=floor(n/2);

 %{
 'm' is the height (or rather 'depth') of the triangle,
 currently only works correctly for odd numbers, 
 will figure out even numbers later
 %}

 hash(1:n)='#';
 fprintf([hash '\n'])

 for row=1:m

    space(1:row)=' ';
    fprintf(space)

    new_hash(1:n-2*row)='#';
    fprintf([new_hash '\n'])

    %{
    that new_hash bit is supposed to shorten the length 
    of hash marks on each iteration, why does this not work??
    %}

 end

So when I input 7, I get:

 #######
  #####
   #####
    #####

But I want to get:

 #######
  #####
   ###
    #

Any help on how to fix this (or an entirely new approach, as long as it uses a for-loop) would be greatly appreciated.

Answer 1

[James Tursa]

You don't set the trailing elements of new_hash to spaces on each iteration, or clear new_hash each iteration, so those trailing hash marks remain. What if you do this:

 for row=1:m
     clear new_hash
         :
        etc

If you are running this as a script, you will want to do this also each iteration:

clear space

Alternatively, you could set these variables directly within your loop and then not have to worry about clearing them each iteration. E.g.,

    space = repmat(' ',1,row);
    new_hash = repmat('#',1,n-2*row);

[Taniel Goetcherian]

Holy crap clear worked, thanks so much! Didn't think it would be this simple. I assumed new_hash would be updated each iteration to its new length.

[James Tursa]

When you use indexing on the left hand side, it is only those specific indexed elements that get changed. All of the other elements remain unchanged.

[Taniel Goetcherian]

Good to know, thanks!