MATLAB Central Newsreader - Zeros some value in array

Zeros some value in array

Jaroslav — Tue, 25 Aug 2009 13:01:05 -0400

Hi,

how could I zeros some numbers in array? I need replace for example first three numbers by zeros, then keep original 2 numbers and then again replace next three numbers by zero etc.
For example, I have array of 10 numbers A=[1:10]
and result would be look like 0 0 0 4 5 0 0 0 9 10

Thanks

Re: Zeros some value in array

Andy — Tue, 25 Aug 2009 13:27:02 -0400

"Jaroslav " <jaroslav.hrebicek@seznam.cz> wrote in message <h70nah$rkk$1@fred.mathworks.com>...
> Hi,
>
> how could I zeros some numbers in array? I need replace for example first three numbers by zeros, then keep original 2 numbers and then again replace next three numbers by zero etc.
> For example, I have array of 10 numbers A=[1:10]
> and result would be look like 0 0 0 4 5 0 0 0 9 10
>
> Thanks

A=1:10;
idx=[1:3 6:8]; % indexes to make zero
A(idx)=0;

Re: Zeros some value in array

Jaroslav — Tue, 25 Aug 2009 19:42:19 -0400

"Andy " <theorigamist@gmail.com> wrote in message <h70or6$ak0$1@fred.mathworks.com>...
> "Jaroslav " <jaroslav.hrebicek@seznam.cz> wrote in message <h70nah$rkk$1@fred.mathworks.com>...
> > Hi,
> >
> > how could I zeros some numbers in array? I need replace for example first three numbers by zeros, then keep original 2 numbers and then again replace next three numbers by zero etc.
> > For example, I have array of 10 numbers A=[1:10]
> > and result would be look like 0 0 0 4 5 0 0 0 9 10
> >
> > Thanks
>
> A=1:10;
> idx=[1:3 6:8]; % indexes to make zero
> A(idx)=0;

Thanks Andy,

but in fact, I will have about 95000 samples. So this way is not what I looking for..

But thank you..

Re: Zeros some value in array

Andy — Tue, 25 Aug 2009 20:27:07 -0400

"Jaroslav " <jaroslav.hrebicek@seznam.cz> wrote in message <h71eqr$6rf$1@fred.mathworks.com>...
> "Andy " <theorigamist@gmail.com> wrote in message <h70or6$ak0$1@fred.mathworks.com>...
> > "Jaroslav " <jaroslav.hrebicek@seznam.cz> wrote in message <h70nah$rkk$1@fred.mathworks.com>...
> > > Hi,
> > >
> > > how could I zeros some numbers in array? I need replace for example first three numbers by zeros, then keep original 2 numbers and then again replace next three numbers by zero etc.
> > > For example, I have array of 10 numbers A=[1:10]
> > > and result would be look like 0 0 0 4 5 0 0 0 9 10
> > >
> > > Thanks
> >
> > A=1:10;
> > idx=[1:3 6:8]; % indexes to make zero
> > A(idx)=0;
>
> Thanks Andy,
>
> but in fact, I will have about 95000 samples. So this way is not what I looking for..
>
> But thank you..

% This approach still works with 95000 samples. You just want to create idx in
% some way other than explicitly choosing which indexes to remove.

% Example: create a vector of random data and remove all values below 0.3:

A=rand(100000,1);
idx=find(A<0.3);
A(idx)=0;

% If you'd like more help doing this, what are your criteria for determining which
% indexes you want to replace with 0?

Re: Zeros some value in array

Jaroslav — Wed, 26 Aug 2009 07:15:08 -0400

"Andy " <theorigamist@gmail.com> wrote in message <h71her$1c6$1@fred.mathworks.com>...
> "Jaroslav " <jaroslav.hrebicek@seznam.cz> wrote in message <h71eqr$6rf$1@fred.mathworks.com>...
> > "Andy " <theorigamist@gmail.com> wrote in message <h70or6$ak0$1@fred.mathworks.com>...
> > > "Jaroslav " <jaroslav.hrebicek@seznam.cz> wrote in message <h70nah$rkk$1@fred.mathworks.com>...
> > > > Hi,
> > > >
> > > > how could I zeros some numbers in array? I need replace for example first three numbers by zeros, then keep original 2 numbers and then again replace next three numbers by zero etc.
> > > > For example, I have array of 10 numbers A=[1:10]
> > > > and result would be look like 0 0 0 4 5 0 0 0 9 10
> > > >
> > > > Thanks
> > >
> > > A=1:10;
> > > idx=[1:3 6:8]; % indexes to make zero
> > > A(idx)=0;
> >
> > Thanks Andy,
> >
> > but in fact, I will have about 95000 samples. So this way is not what I looking for..
> >
> > But thank you..
>
> % This approach still works with 95000 samples. You just want to create idx in
> % some way other than explicitly choosing which indexes to remove.
>
> % Example: create a vector of random data and remove all values below 0.3:
>
> A=rand(100000,1);
> idx=find(A<0.3);
> A(idx)=0;
>
> % If you'd like more help doing this, what are your criteria for determining which
> % indexes you want to replace with 0?

It does not matter, what indexes will be replaced with 0. But the number of 0 must be always same and this interval of zeros should be repeated randomly or periodically up to end of samples (in array).

Re: Zeros some value in array

Lorenzo Guerrasio — Wed, 26 Aug 2009 08:47:03 -0400

I'm not sure if I got what you want. take a look, maybe it helps. It's not the best solution, probably.

my_seq=[0 0 1 1 0];%here you put the sequence of zero you like
my_vect=rand(1,54353);
Nrep=floor(length(my_vect)/length(my_seq));
my_mask=repmat(my_seq,1,Nrep);
my_mask=[my_mask,my_seq(1:(length(my_vect)-length(my_mask)))];
new_vect=my_vect.*my_mask;

"Jaroslav " <jaroslav.hrebicek@seznam.cz> wrote in message <h70nah$rkk$1@fred.mathworks.com>...
> Hi,
>
> how could I zeros some numbers in array? I need replace for example first three numbers by zeros, then keep original 2 numbers and then again replace next three numbers by zero etc.
> For example, I have array of 10 numbers A=[1:10]
> and result would be look like 0 0 0 4 5 0 0 0 9 10
>
> Thanks

Re: Zeros some value in array

us — Wed, 26 Aug 2009 08:50:18 -0400

"Jaroslav "
> It does not matter, what indexes will be replaced with 0. But the number of 0 must be always same and this interval of zeros should be repeated randomly or periodically up to end of samples (in array)...

one of the solutions
- for the rand case...

     n=4; % <- #data to replace with zeros
     v=1:10;
     ix=randperm(numel(v));
     v(ix(1:n))=0;

us

Re: Zeros some value in array

us — Wed, 26 Aug 2009 09:03:19 -0400

"us " <us@neurol.unizh.ch> wrote in message <h72t0a$9je$1@fred.mathworks.com>...
> "Jaroslav "
> > It does not matter, what indexes will be replaced with 0. But the number of 0 must be always same and this interval of zeros should be repeated randomly or periodically up to end of samples (in array)...
>
> one of the solutions
> - for the rand case...
>
> n=4; % <- #data to replace with zeros
> v=1:10;
> ix=randperm(numel(v));
> v(ix(1:n))=0;
>
> us

unfortunately, the second part got lost in the copy/paste process...

one of the solutions
- for the rand case...
...
- for the periodic case

     v=1:16;
     tmpl=[0,0,1,1]; % <- min block of zeros/data with numel(v) = N x numel(tmpl)!
     r=reshape(bsxfun(@times,reshape(v,numel(tmpl),[]).',tmpl).',1,[]);
     disp([v;r]);
%{
          1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
          0 0 3 4 0 0 7 8 0 0 11 12 0 0 15 16
%}

us