Matlab does wired stuff

This is part of a function that is doing what i called wired. The vector 'dim_set' in this snippet should expanded on both side depending on the value of the scalar 'const'. I have no idea while the result is wired. Pls help!

 % expand dim_set by 1 or a const on each side
           dim_set=[67.5:100.5];
           const=20;
           dim_set %befor
           dim_set=floor(dim_set);
            if(dim_set(1)>1)
                dim_set=[dim_set(1)-const:dim_set(1),dim_set];
            end
            dim_set=[dim_set,dim_set(end):dim_set(end)+const];
           % See befoer and after values of dim_set to see this
           dim_set %after

[bethel o]

Hmm i have just ran this snippet on the command window and it just worked fine, but the exact code is refusing to work in my function

[Sean de Wolski]

Do you have a question?

[Andreas Goser]

I can't resist: Is it wired ot weird?

[bethel o]

sorry my question is, why dim_set output not right when ran inside my function, but hover works when i change the scalar 'const' from 20 to 1. I will post the function

[bethel o]

@Andreas Goser. i meant weird. I have been coding for stegers algorithm constantly for one week now, so am tired. And by the way is it 'ot weird' or 'or weird'?. lol there

[Andreas Goser]

I noticed that :-) - can't edit the comments

Answer 1

[Paulo Silva]

dim_set=67.5:1:100.5
const=20;
dim_set %before
dim_set=floor(dim_set); %have no clue what's the purpose of this line
dim_set=[dim_set(1)-const:dim_set(1)-1 dim_set]; %expand left
dim_set=[dim_set dim_set(end)+1:dim_set(end)+const]; %expand right
% See before and after values of dim_set to see this
dim_set %after

[bethel o]

thanks Paulo but this dim_set=floor(dim_set); is needed to as i only want integer values for the next part of the function. I have just post the complete function. Thanks again

[bethel o]

I see your solution cares the duplications but this duplicate are fine. The issue is that the result i get is completely wrong

[Paulo Silva]

no the duplicated values aren't fine, when you expand something the borders shouldn't be duplicated

[bethel o]

yep cheers that one is corrected. but the issue remains.

[Paulo Silva]

You were correct, now that I know what your function does I came to the conclusion that the borders are irrelevant but there's no need to waste a little more memory with duplicated values.

Answer 2

[bethel o]

   function tf=intersect_l(dim_set,memb)
           % expand dim_set by 1 or a const on each side
           %dim_set=[67.5:100.5];
           const=20;
           dim_set %befor
           dim_set=floor(dim_set);
            if(dim_set(1)>1)
                dim_set=[dim_set(1)-const:dim_set(1),dim_set];
            end
            dim_set=[dim_set,dim_set(end):dim_set(end)+const];
           dim_set %after 
            if(intersect(dim_set,memb))
                tf=1;
            else
                tf=0;
            end
        end

[Paulo Silva]

You are mixing the function and the function call in the same code and you don't explain exactly the purpose of your function.

Are you trying to see if dim_set is present inside memb?

[bethel o]

sorry again. am trying to see if memb is present in dim_set. memb is just a scalar and dim_set is a vector. But the part that is misbehaving is the part befor the

if(intersect(dim_set,memb))

tf=1;

else

tf=0;

end

[Paulo Silva]

just use the matlab ismember function

doc ismember

[Paulo Silva]

or even better

tf=isempty(dim_set(dim_set==memb))

[Paulo Silva]

I forget the negation ~, this way should work

tf=~isempty(dim_set(dim_set==memb))

[bethel o]

but the problematic part is the part that expands the dim_set. dim_set needs to be expanded. I have been coding regularly in matlab for over a year now but the output of that simple function is just weird. You can try the function while checking the values of dim_set for before and after expansion. I was thinking that some1 can pick up what i am doing fundamentally wrong.

[Paulo Silva]

Seem to be working fine here with all the changes I suggested

[bethel o]

Thanks a lot Paulo. I have also tried it and it works, outside of its parent function (because its a sub function). I have no idea why it dosn't work for certain values of 'const' when ran through the parent function but works for all values of 'const' when ran as a function on its own.

I will have a sleep and come back to it.

Thanks alot for your assistance.

Bethel

[bethel o]

Hey Paulo, I did not realize that in programing if I have something like

IF(i && j), j will not be checked if i =false . this was simply the problem I was having. I was checking the output of j and only saw it some times (i and j are functions that returns boolean in my program). I did not know that the reason I was not seeing j sometimes was because sometimes i =false.