Re: array cell...... Find index from value

[Przemek Klosowski]

On 07/25/2018 03:15 PM, shivax wrote:
> i writed GG as example.
> But i need to execute code on this array cell:
>
> GG
>   [7,2] =
>
>
> here there is several null cells..
>
>
> i've try this code:
>
> > > a = cellfun (@(x) ~isempty (x) && (x ==122), string_dat_rp(:,2));
> > > find(a, 1, 'first')
>
> ans = [](0x1)
First, take a look at how Markus wrote his example: you can literally 
start a fresh version of Octave and paste a copy of his code into it. 
You give some results, but I had to reverse-engineer them to populate 
the cell array the way I think you have it. I think I got it right, but 
please try to come up with a nice compact example so that everyone can 
follow and replicate it.
For instance, there's no point in using large indices like {54,2}---it 
just results in large output printouts. Why not use
GG{3,2}=120
GG{5,2}=122

Next, can you give a brief background as to why you're using cell 
arrays? THis is an advanced topic, and most  numerical code just uses 
regular arrays (eg. Gx(3,2)=6). Cell arrays are useful when your arrays 
are weird, like when they contain  submatrices of different size or even 
dimension---this doesn't seem to be the case for you.

Then, you seem to be looking for an associative array---looking for an 
index of a cell containing a specific value. Perhaps you could write 
your code accordingly---maybe, if your specific values are indeed small 
integers, use THEM as indices and store the coordinates : HH(120) = 54; 
HH(123)=23

Then, assuming you really want to work with cell arrays, you can play 
with various indexing modes: for instance observe the difference between 
GG{3,2} and GG(3,2).
Octave is interactive, so you're supposed to build longer expressions by 
trying their pieces on your data.
For instance, since GG(3,2) returns cells,  you can do a=GG(:,2) and 
then look at the result:
    whos a GG
and it'll tell you that they both are cell arrays. You can then use 
cellfun, and adapt the @(X) function to do what you need to do.
Again, however, it would be best if you tried to explain (with concrete, 
self-contained examples) what do you want to do.