Thread Subject: Deleting cells

Hello,

I have a problem, it may be simple but im cant figure out
how to delete cells in a large matrix.

For example.
-5 -1 -5 -1 -5
-4 -4 -4 -4 -4
-3 -3 -3 -3 -3
-2 -2 -2 -2 -2
-1 -1 -1 -1 -1
0 0 0 0 0
1 1 1 1 1
2 2 2 2 2
3 3 3 3 3
4 3 4 3 4
5 1 5 1 5



If the above is a matrix and I am trying to delete cells
and their corresponding rows with values out of the range
of (-3 < A < 3). I have tried
 A= [The above Matrix}
q=find(sum((A)>3));
A(q:end)=[];
 

But the above deletes all the matrix.
I have tried the below to find the first occurrence.

>> q=find(A>3,1)
A(q,:)=[]

But this only deletes one row and gives the below answer.

-5 -5 -5 -5 -5
-4 -4 -4 -4 -4
-3 -3 -3 -3 -3
-2 -2 -2 -2 -2
-1 -1 -1 -1 -1
0 0 0 0 0
1 1 1 1 1
2 2 2 2 2
3 3 3 3 3
5 5 5 5 5



What I am finally trying to achieve is the below matrix.

-3 -3 -3 -3 -3
-2 -2 -2 -2 -2
-1 -1 -1 -1 -1
0 0 0 0 0
1 1 1 1 1
2 2 2 2 2
3 3 3 3 3


Thanks

"Ali Hussain" <hussaizj@aston.ac.uk> wrote in message
<g37vap$81f$1@fred.mathworks.com>...
> Hello,
>
> I have a problem, it may be simple but im cant figure out
> how to delete cells in a large matrix.
>
> For example.
> -5 -1 -5 -1 -5
> -4 -4 -4 -4 -4
> -3 -3 -3 -3 -3
> -2 -2 -2 -2 -2
> -1 -1 -1 -1 -1
> 0 0 0 0 0
> 1 1 1 1 1
> 2 2 2 2 2
> 3 3 3 3 3
> 4 3 4 3 4
> 5 1 5 1 5
>
>
>
> If the above is a matrix and I am trying to delete cells
> and their corresponding rows with values out of the range
> of (-3 < A < 3). I have tried
> A= [The above Matrix}
> q=find(sum((A)>3));
> A(q:end)=[];
>
>
> But the above deletes all the matrix.
> I have tried the below to find the first occurrence.
>
> >> q=find(A>3,1)
> A(q,:)=[]
>
> But this only deletes one row and gives the below answer.
>
> -5 -5 -5 -5 -5
> -4 -4 -4 -4 -4
> -3 -3 -3 -3 -3
> -2 -2 -2 -2 -2
> -1 -1 -1 -1 -1
> 0 0 0 0 0
> 1 1 1 1 1
> 2 2 2 2 2
> 3 3 3 3 3
> 5 5 5 5 5
>
>
>
> What I am finally trying to achieve is the below matrix.
>
> -3 -3 -3 -3 -3
> -2 -2 -2 -2 -2
> -1 -1 -1 -1 -1
> 0 0 0 0 0
> 1 1 1 1 1
> 2 2 2 2 2
> 3 3 3 3 3
>
>
> Thanks
>
>
Hi
Maybe this would work :
idx=abs(max(A,[],1))>3;
A(idx,:)=[]

Caroline

A=[ -5 -1 -5 -1 -5; ...
    -4 -4 -4 -4 -4; ...
   -3 -3 -3 -3 -3; ...
 -2 -2 -2 -2 -2; ...
 -1 -1 -1 -1 -1; ...
 0 0 0 0 0; ...
 1 1 1 1 1; ...
 2 2 2 2 2; ...
 3 3 3 3 3; ...
 4 3 4 3 4; ...
 5 1 5 1 5];
%note that
%sum(A)
%
%ans =
%
% 0 -1 0 -1 0
% sum(A,2)
%
% ans =
%
% -17
% -20
% -15
% -10
% -5
% 0
% 5
% 10
% 15
% 18
% 17

% save what you need, not delete what u don't
q=find((sum(A,2)>=-15) & (sum(A,2)<=15))

A=A(q,:)

"French Caro " <caro95470@nospam.free.fr> wrote in message
<g38032$ed3$1@fred.mathworks.com>...
> "Ali Hussain" <hussaizj@aston.ac.uk> wrote in message
> <g37vap$81f$1@fred.mathworks.com>...
> > Hello,
> >
> > I have a problem, it may be simple but im cant figure
out
> > how to delete cells in a large matrix.
> >
> > For example.
> > -5 -1 -5 -1 -5
> > -4 -4 -4 -4 -4
> > -3 -3 -3 -3 -3
> > -2 -2 -2 -2 -2
> > -1 -1 -1 -1 -1
> > 0 0 0 0 0
> > 1 1 1 1 1
> > 2 2 2 2 2
> > 3 3 3 3 3
> > 4 3 4 3 4
> > 5 1 5 1 5
> >
> >
> >
> > If the above is a matrix and I am trying to delete
cells
> > and their corresponding rows with values out of the
range
> > of (-3 < A < 3). I have tried
> > A= [The above Matrix}
> > q=find(sum((A)>3));
> > A(q:end)=[];
> >
> >
> > But the above deletes all the matrix.
> > I have tried the below to find the first occurrence.
> >
> > >> q=find(A>3,1)
> > A(q,:)=[]
> >
> > But this only deletes one row and gives the below
answer.
> >
> > -5 -5 -5 -5 -5
> > -4 -4 -4 -4 -4
> > -3 -3 -3 -3 -3
> > -2 -2 -2 -2 -2
> > -1 -1 -1 -1 -1
> > 0 0 0 0 0
> > 1 1 1 1 1
> > 2 2 2 2 2
> > 3 3 3 3 3
> > 5 5 5 5 5
> >
> >
> >
> > What I am finally trying to achieve is the below matrix.
> >
> > -3 -3 -3 -3 -3
> > -2 -2 -2 -2 -2
> > -1 -1 -1 -1 -1
> > 0 0 0 0 0
> > 1 1 1 1 1
> > 2 2 2 2 2
> > 3 3 3 3 3
> >
> >
> > Thanks
> >
> >
> Hi
> Maybe this would work :
> idx=abs(max(A,[],1))>3;
> A(idx,:)=[]
>
> Caroline



Hi,

I have tried the above code and it worked only when I
changed the dimension from 1 to 2(as in the code below).
Is there a way that this can be changed so i can
automatically specify the dimension as its used for a
1024x168 double matrix.

>> idx=abs(max(Sheet1,[],2))>3;
>> Sheet1(idx,:)=[]

Thanks

"Ali Hussain" <hussaizj@aston.ac.uk> wrote in message
<snip>
>
> Hi,
>
> I have tried the above code and it worked only when I
> changed the dimension from 1 to 2(as in the code below).
> Is there a way that this can be changed so i can
> automatically specify the dimension as its used for a
> 1024x168 double matrix.
>
> >> idx=abs(max(Sheet1,[],2))>3;
> >> Sheet1(idx,:)=[]
>
> Thanks

Yes I was not sure of the third argument.
What do you mean by "Is there a way that this can be changed
so i can automatically specify the dimension" ?

In this formula the dimension is not used.
It will work for any N*M matrix.
The 2 in max(A,[],2) just indicates the dimension along
where max is done (not sure I'm very clear on this sorry)

Caroline

"French Caro " <caro95470@nospam.free.fr> wrote in message
<g383c2$938$1@fred.mathworks.com>...
> "Ali Hussain" <hussaizj@aston.ac.uk> wrote in message
> <snip>
> >
> > Hi,
> >
> > I have tried the above code and it worked only when I
> > changed the dimension from 1 to 2(as in the code
below).
> > Is there a way that this can be changed so i can
> > automatically specify the dimension as its used for a
> > 1024x168 double matrix.
> >
> > >> idx=abs(max(Sheet1,[],2))>3;
> > >> Sheet1(idx,:)=[]
> >
> > Thanks
>
> Yes I was not sure of the third argument.
> What do you mean by "Is there a way that this can be
changed
> so i can automatically specify the dimension" ?
>
> In this formula the dimension is not used.
> It will work for any N*M matrix.
> The 2 in max(A,[],2) just indicates the dimension along
> where max is done (not sure I'm very clear on this sorry)
>
> Caroline

I have tried it again with adding extra rows of data. I
see what it means by dimension(of the matrix).

Thanks again

> > Hi,
> >
> > I have tried the above code and it worked only when I
> > changed the dimension from 1 to 2(as in the code
below).
> > Is there a way that this can be changed so i can
> > automatically specify the dimension as its used for a
> > 1024x168 double matrix.
> >
> > >> idx=abs(max(Sheet1,[],2))>3;
> > >> Sheet1(idx,:)=[]
> >
> > Thanks
>
> Yes I was not sure of the third argument.
> What do you mean by "Is there a way that this can be
changed
> so i can automatically specify the dimension" ?
>
> In this formula the dimension is not used.
> It will work for any N*M matrix.
> The 2 in max(A,[],2) just indicates the dimension along
> where max is done (not sure I'm very clear on this sorry)
>
> Caroline

Hi,

Thank you for the response...

I am also trying to do the same for another matrix

-5 -4 -3 -2 -1 0 1 2 3 4 5
-1 -4 -3 -2 -1 0 1 2 3 4 5
-5 -4 -3 -2 -1 0 1 2 3 4 5
-1 -4 -3 -2 -1 0 1 2 3 4 5
-5 -4 -3 -2 -1 0 1 2 3 4 5

This time im deleting columns. range (-3<A<3)

Is it possible to do that?

Thanks

  

"Ali Hussain" <hussaizj@aston.ac.uk> wrote in message
<g38hjm$ou7$1@fred.mathworks.com>...
> > > Hi,
> > >
> > > I have tried the above code and it worked only when I
> > > changed the dimension from 1 to 2(as in the code
> below).
> > > Is there a way that this can be changed so i can
> > > automatically specify the dimension as its used for a
> > > 1024x168 double matrix.
> > >
> > > >> idx=abs(max(Sheet1,[],2))>3;
> > > >> Sheet1(idx,:)=[]
> > >
> > > Thanks
> >
> > Yes I was not sure of the third argument.
> > What do you mean by "Is there a way that this can be
> changed
> > so i can automatically specify the dimension" ?
> >
> > In this formula the dimension is not used.
> > It will work for any N*M matrix.
> > The 2 in max(A,[],2) just indicates the dimension along
> > where max is done (not sure I'm very clear on this sorry)
> >
> > Caroline
>
> Hi,
>
> Thank you for the response...
>
> I am also trying to do the same for another matrix
>
> -5 -4 -3 -2 -1 0 1 2 3 4 5
> -1 -4 -3 -2 -1 0 1 2 3 4 5
> -5 -4 -3 -2 -1 0 1 2 3 4 5
> -1 -4 -3 -2 -1 0 1 2 3 4 5
> -5 -4 -3 -2 -1 0 1 2 3 4 5
>
> This time im deleting columns. range (-3<A<3)
>
> Is it possible to do that?
>
> Thanks
>
Of course it is just the transpose.
btw you should have done it by transposing your matrix twice
but it is not the more efficient way.

So this should work :
idx=abs(max(A,[],1))>3;
A(:,idx)=[]

"French Caro " <caro95470@nospam.free.fr> wrote in message
<g38i2m$16b$1@fred.mathworks.com>...



Hi,

I have rotated the Matrix using the below code,

th=30*pi/180; %angle of rotation;
Rz=[cos(th) -sin(th) 0;sin(th) cos(th) 0;0 0 1];
P=[x(:) y(:) z1(:)]*Rz; %rotate each point on surface
x=reshape(P(:,1),size0);%transform surface vertices back
into matrix
y=reshape(P(:,2),size0);
z1=reshape(P(:,3),size0);


I am having problems with using the

idx=abs(max(A,[],1))>3;
A(:,idx)=[]

as it shapes the original matrix rather than the rotated
matrix. Is there any way I can cut the rotated matrix.

Thanks