Thread Subject: intersection for long list of cells

Hi all, I have two long lists of strings in cells (each
25K entries long) and I'd like to find the indices of
entries that are common between both lists.

I'm hoping to find a faster way of doing this than an
individual search (which takes way to long given the size
of the lists)

Thanks!

"Chris " <cag44@removethispitt.edu> wrote in message <fu42p1
$o5k$1@fred.mathworks.com>...
> Hi all, I have two long lists of strings in cells (each
> 25K entries long) and I'd like to find the indices of
> entries that are common between both lists.
>
> I'm hoping to find a faster way of doing this than an
> individual search (which takes way to long given the size
> of the lists)
>
> Thanks!

help intersect

Jos

Hi Jos,

Intersect doesn't operate on cells.


"Jos " <DELjos@jasenDEL.nl> wrote in message
<fu45ub$97b$1@fred.mathworks.com>...
> "Chris " <cag44@removethispitt.edu> wrote in message
<fu42p1
> $o5k$1@fred.mathworks.com>...
> > Hi all, I have two long lists of strings in cells
(each
> > 25K entries long) and I'd like to find the indices of
> > entries that are common between both lists.
> >
> > I'm hoping to find a faster way of doing this than an
> > individual search (which takes way to long given the
size
> > of the lists)
> >
> > Thanks!
>
> help intersect
>
> Jos

"Chris " <cag44@removethispitt.edu> wrote in message
<fu4se9$oh9$1@fred.mathworks.com>...

> "Jos " <DELjos@jasenDEL.nl> wrote in message
> <fu45ub$97b$1@fred.mathworks.com>...
> > "Chris " <cag44@removethispitt.edu> wrote in message
> <fu42p1
> > $o5k$1@fred.mathworks.com>...
> > > Hi all, I have two long lists of strings in cells
> (each
> > > 25K entries long) and I'd like to find the indices of
> > > entries that are common between both lists.
> > >
> > > I'm hoping to find a faster way of doing this than an
> > > individual search (which takes way to long given the
> size
> > > of the lists)
> > >
> > > Thanks!
> >
> > help intersect
> >
> > Jos
>
> Hi Jos,
>
> Intersect doesn't operate on cells.
>
>

(fixed top-posting)

Apparently you mean something else then "I have two long
lists of strings in cells (each 25K entries long) and I'd
like to find the indices of entries that are common between
both lists.", since:

A = {'a','b','c'} ;
B = {'a','b','d'} ;
intersect(A,B)
ans =

    'a' 'b'

Can you give a small(!!) example of the inputs and the
desired output?

Jos

the help says:

INTERSECT(A,B)
A and B can be cell arrays of strings.
and this one works on my machine:

for n = 1:20
    t{n} = num2str(n+10);
    tt{n} = num2str(n+10);
end
intersect(t,tt)



"Chris " <cag44@removethispitt.edu> wrote in message
<fu4se9$oh9$1@fred.mathworks.com>...
> Hi Jos,
>
> Intersect doesn't operate on cells.
>
>
> "Jos " <DELjos@jasenDEL.nl> wrote in message
> <fu45ub$97b$1@fred.mathworks.com>...
> > "Chris " <cag44@removethispitt.edu> wrote in message
> <fu42p1
> > $o5k$1@fred.mathworks.com>...
> > > Hi all, I have two long lists of strings in cells
> (each
> > > 25K entries long) and I'd like to find the indices of
> > > entries that are common between both lists.
> > >
> > > I'm hoping to find a faster way of doing this than an
> > > individual search (which takes way to long given the
> size
> > > of the lists)
> > >
> > > Thanks!
> >
> > help intersect
> >
> > Jos
>

Hello Jos,

This is weird, tried it again after rebooting and it
worked. Checked the exact same set of commands was giving
me an error before. Thanks for the help

"Jos " <DELjos@jasenDEL.nl> wrote in message <fu4t12
$d8u$1@fred.mathworks.com>...
> "Chris " <cag44@removethispitt.edu> wrote in message
> <fu4se9$oh9$1@fred.mathworks.com>...
>
> > "Jos " <DELjos@jasenDEL.nl> wrote in message
> > <fu45ub$97b$1@fred.mathworks.com>...
> > > "Chris " <cag44@removethispitt.edu> wrote in message
> > <fu42p1
> > > $o5k$1@fred.mathworks.com>...
> > > > Hi all, I have two long lists of strings in cells
> > (each
> > > > 25K entries long) and I'd like to find the indices
of
> > > > entries that are common between both lists.
> > > >
> > > > I'm hoping to find a faster way of doing this than
an
> > > > individual search (which takes way to long given
the
> > size
> > > > of the lists)
> > > >
> > > > Thanks!
> > >
> > > help intersect
> > >
> > > Jos
> >
> > Hi Jos,
> >
> > Intersect doesn't operate on cells.
> >
> >
>
> (fixed top-posting)
>
> Apparently you mean something else then "I have two long
> lists of strings in cells (each 25K entries long) and I'd
> like to find the indices of entries that are common
between
> both lists.", since:
>
> A = {'a','b','c'} ;
> B = {'a','b','d'} ;
> intersect(A,B)
> ans =
>
> 'a' 'b'
>
> Can you give a small(!!) example of the inputs and the
> desired output?
>
> Jos

Chris schreef:
> Hi all, I have two long lists of strings in cells (each
> 25K entries long) and I'd like to find the indices of
> entries that are common between both lists.
>
> I'm hoping to find a faster way of doing this than an
> individual search (which takes way to long given the size
> of the lists)
>
> Thanks!

Maybe you can have a look at the binary tree object named BTree in the GSTools
toolbox. You can find it on the matlab file exchange server:

http://tinyurl.com/2f8cll

You can use something like
tree1=BTree(list1);
tree2=BTree(list2);
tmp = intersect(unique(list1), unique(list2))
for i=1:length(tmp)
res1=getitem(tree1, tmp{i});
res2=getitem(tree2, tmp{i});
positions{i,1} = cat(1,res1.itemvalues{:});
positions{i,2} = cat(1,res2.itemvalues{:});
end


The result is found in positions and this solution should work with stringlists,
numeric vectors and 1D cell arrays with both numbers and strings.

Regards
Kris