Re: Wrong indices returned using Lookup for cells containing strings

[Nicholas Jankowski]

On Tue, Oct 20, 2015 at 8:42 AM, Olaf Till <address@hidden> wrote:

On Tue, Oct 20, 2015 at 08:25:21AM -0400, Nicholas Jankowski wrote:
> On Tue, Oct 20, 2015 at 8:06 AM, Olaf Till <address@hidden> wrote:
>
> > On Tue, Oct 20, 2015 at 02:37:15AM -0700, rcharan51 wrote:
> > > i have two cell arrays(strings) of size 20X1 and 3X1. when i tried to
> > lookup
> > > larger cell array in the shorter one the indices returned are not
> > correct.
> > > My guess is that since the cells in the short array are not sorted in any
> > > particular order, wrong indices are returned. Am i right? if so what is
> > work
> > > around for this?
> > > any help is much appreciated. Thanks.
> > >
> > > >> b=geo_ch(1:20, 1)
> > > b =
> > > {
> > >   [1,1] = GEN
> > >   [2,1] = GEN
> > >   [3,1] = GEN
> > >   [4,1] = GEN
> > >   [5,1] = GEN
> > >   [6,1] = GEN
> > >   [7,1] = GEN
> > >   [8,1] = GEN
> > >   [9,1] = GEN
> > >   [10,1] = GEN
> > >   [11,1] = GEN
> > >   [12,1] = GEN
> > >   [13,1] = GEN
> > >   [14,1] = GEN
> > >   [15,1] = GEN
> > >   [16,1] = GEN
> > >   [17,1] = WEAK
> > >   [18,1] = WEAK
> > >   [19,1] = WEAK
> > >   [20,1] = WEAK
> > > }
> > > >> a=trop1mix(4:6,1)
> > > a =
> > > {
> > >   [1,1] = GEN
> > >   [2,1] = WEAK
> > >   [3,1] = MIX
> > > }
> > > >> id=lookup(a,b)
> > > id =
> > >
> > >    1
> > >    1
> > >    1
> > >    1
> > >    1
> > >    1
> > >    1
> > >    1
> > >    1
> > >    1
> > >    1
> > >    1
> > >    1
> > >    1
> > >    1
> > >    1
> > >    3
> > >    3
> > >    3
> > >    3
> >
> > But the above seems correct to me ... Olaf
> >
> >
> I assume he's expecting 1's followed by 2's. I've never used lookup for
> non-numerical arrays, but I know it generally expects a to be monotonic.
> the help says for strings "lookup is performed using lexicographical
> comparison".  I notice his a is 'lexocographically' monotonic but b is
> not.  is that the source of his confusion?  Olaf, can you explain why the
> output of 3 should be expected, rather than the 2 he was expecting?

No, I can't. I just mixed it up in my head. That's the second time
today, seems it's not my day ... And you are surely right with the
table having to be monotonic. So 'a = sort (a)' should solve the
problem ...

Nope. lookup(sort(a),b) produces the same output.

Also, I was curious to see if Matlab produced the same results. turns out it errors when presented with cell arrays.

>> id = lookup(a,b)
Undefined function 'lookup' for input arguments of type 'cell'.