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From: Gerardo on 16 Jul 2010 02:36
Apologies for the basic question, but as a fairly new user I just cannot figure this out.

I have two tables with thousands of rows, for both the first column is time. Some of the times (rows) in the second table are also present in the first table. I need to find those rows and append the values as new columns in the first table.

As an example:

A=[1 10 100;
2 20 200;
3 30 300;
4 40 400;
...];

B=[1.5 15 150;
2 0 20000;
3.5 0 35000;
4 0 40000;
...];

Resulting table=

C=[1 10 100 NaN;
2 20 200 20000;
3 30 300 NaN;
4 40 400 40000;
...];

I tried using "ismember", and works fine when Size(Table1)>Size(Table2). When Table2 has more rows, it doesn't work.
I also tried splitting a longer Table2 in two tables so they are smaller than Table1, but still didn't work, meaning that it is not consistent.

I will really appreciate any comments, suggestions.

Thanks,

Antony
From: Oleg on 16 Jul 2010 03:26
> I tried using "ismember", and works fine when Size(Table1)>Size(Table2). When Table2 has more rows, it doesn't work.
> I also tried splitting a longer Table2 in two tables so they are smaller than Table1, but still didn't work, meaning that it is not consistent.
>
> I will really appreciate any comments, suggestions.
>
> Thanks,
>
> Antony

I modified slightly A and B so that the rows in B are more than in A.

A=[1 10 100;
2 20 200;
3 30 300;
4 40 400];

B=[ 1 1 20 % added row
1.5 15 150;
2 0 20000;
3.5 0 35000;
4 0 40000;]

% Preallocate
A = [A, NaN(size(A,1),1)];

% Use ismember
[tf,loc] = ismember(B(:,1),A(:,1));

A(loc(loc~=0),4) = B(tf,3)

Oleg
From: Gerardo on 16 Jul 2010 04:15
"Oleg " <oleg.komarovRemoveThis(a)hotmail.it> wrote in message <i1p1id$6l6$1(a)fred.mathworks.com>...
> > I tried using "ismember", and works fine when Size(Table1)>Size(Table2). When Table2 has more rows, it doesn't work.
> > I also tried splitting a longer Table2 in two tables so they are smaller than Table1, but still didn't work, meaning that it is not consistent.
> >
> > I will really appreciate any comments, suggestions.
> >
> > Thanks,
> >
> > Antony
>
> I modified slightly A and B so that the rows in B are more than in A.
>
> A=[1 10 100;
> 2 20 200;
> 3 30 300;
> 4 40 400];
>
> B=[ 1 1 20 % added row
> 1.5 15 150;
> 2 0 20000;
> 3.5 0 35000;
> 4 0 40000;]
>
> % Preallocate
> A = [A, NaN(size(A,1),1)];
>
> % Use ismember
> [tf,loc] = ismember(B(:,1),A(:,1));
>
> A(loc(loc~=0),4) = B(tf,3)
>
> Oleg


Oleg,

Thanks a million. It works perfectly.

Antony
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