Thread Subject: Help. I'm stuck on repeating for-loop.

The concept is really simple but I can't write the for-loop
that will do the job. In the for-loop, the upper limit
changes incrementally from 1 to 1000 and the results are
dumped into a matrix. Then these matrices are put into a
single cell. See below.

for i = 1 : 1;
    A1(i,1) = B(i,1);
end

for i = 1 : 2; %increments of 1; i.e., 1,2,3,4...1000
    A2(i,1) = B(i,1);
end

for i = 1 : 1000; %last value
    A1000(i,1) = B(i,1);
end

wrap = {A1, A2, A3, A4, A5 ..., A1000}
Obviously, you're not going to type it a 1000 times over.
But can't find an easier way to do this. I've gotten this,
but obviously it doesn't work:
for i = 1 : 1000;
    A{i,1}(i,1) = B(i,1);
end

Any help?

for ii = 1:1000
   A(ii,1) = B(ii,1);
end

You were close. Hope that helps.

NO. No offense, but you didn't read problem carefully. The code:
> for ii = 1:1000
> A(ii,1) = B(ii,1);
> end
will return just one matrix with a thousand rows.
What is required is a thousand matrices with the first
matrix having just 1 value (1 row), and the second matrix
having 2 rows, and the third matrix having 3 rows and so
forth up to 1000. Then these matrix are put into a cell. I
just don't know how to do it without typing it out a
thousand for loops - although the real solution is probably
a joke to a seasoned Matlab user.



"Ken Fleisher" <k-fleisher.donotspamme@nga.gov> wrote in
message <fljimo$9p$1@fred.mathworks.com>...
> for ii = 1:1000
> A(ii,1) = B(ii,1);
> end
>
> You were close. Hope that helps.

On Jan 3, 3:55 pm, "mat lav"
<mattylaver.delete.this.nosp...@gmail.com> wrote:
> The concept is really simple but I can't write the for-loop
> that will do the job. In the for-loop, the upper limit
> changes incrementally from 1 to 1000 and the results are
> dumped into a matrix. Then these matrices are put into a
> single cell. See below.
>
> for i = 1 : 1;
> A1(i,1) = B(i,1);
> end
>
> for i = 1 : 2; %increments of 1; i.e., 1,2,3,4...1000
> A2(i,1) = B(i,1);
> end
>
> for i = 1 : 1000; %last value
> A1000(i,1) = B(i,1);
> end
>
> wrap = {A1, A2, A3, A4, A5 ..., A1000}

If these are going to end up in a cell array, why define
the individual variables A1, A2, ...? Why not put
The values directly into your cell array?

> Obviously, you're not going to type it a 1000 times over.
> But can't find an easier way to do this. I've gotten this,
> but obviously it doesn't work:
> for i = 1 : 1000;
> A{i,1}(i,1) = B(i,1);

Try A{i} = B(1:i, 1);

> end

           - Randy

Randy Poe <poespam-trap@yahoo.com> wrote in message
<2f17e9ce-08c6-4fec-beca-
6be40cc1a29c@c4g2000hsg.googlegroups.com>...
> On Jan 3, 3:55 pm, "mat lav"
> <mattylaver.delete.this.nosp...@gmail.com> wrote:
> > The concept is really simple but I can't write the for-
loop
> > that will do the job. In the for-loop, the upper limit
> > changes incrementally from 1 to 1000 and the results are
> > dumped into a matrix. Then these matrices are put into a
> > single cell. See below.
> >
> > for i = 1 : 1;
> > A1(i,1) = B(i,1);
> > end
> >
> > for i = 1 : 2; %increments of 1; i.e., 1,2,3,4...1000
> > A2(i,1) = B(i,1);
> > end
> >
> > for i = 1 : 1000; %last value
> > A1000(i,1) = B(i,1);
> > end
> >
> > wrap = {A1, A2, A3, A4, A5 ..., A1000}
>
> If these are going to end up in a cell array, why define
> the individual variables A1, A2, ...? Why not put
> The values directly into your cell array?
>
> > Obviously, you're not going to type it a 1000 times
over.
> > But can't find an easier way to do this. I've gotten
this,
> > but obviously it doesn't work:
> > for i = 1 : 1000;
> > A{i,1}(i,1) = B(i,1);
>
> Try A{i} = B(1:i, 1);
>
> > end
>
> - Randy


I think Randy has it right. But if you really want to do
it the hard way, see Question 3.6 of the MATLAB FAQ at:

http://www.mit.edu/~pwb/cssm/matlab-faq_toc.html

In article <fljmel$4a5$1@fred.mathworks.com>,
mat lav <mattylaver.delete.this.nospamy@gmail.com> wrote:

>What is required is a thousand matrices with the first
>matrix having just 1 value (1 row), and the second matrix
>having 2 rows, and the third matrix having 3 rows and so
>forth up to 1000. Then these matrix are put into a cell. I
>just don't know how to do it without typing it out a
>thousand for loops - although the real solution is probably
>a joke to a seasoned Matlab user.

If the above is your requirement, then either type out the
thousand for loops or use a program or editor to generate them
for you.

I would suggest, though, that you modify your strategy so that
instead of using matrices with 1 row, 2 rows, etc., that you use
a single cell, the K'th entry of which is the matrix with K rows.
Something along the lines of,

for K=1:1000
  A{K} = B(1:K,1);
end
--
   "Any sufficiently advanced bug is indistinguishable from a feature."
   -- Rich Kulawiec

"mat lav" <mattylaver.delete.this.nospamy@gmail.com> writes:

> The concept is really simple but I can't write the for-loop
> that will do the job. In the for-loop, the upper limit
> changes incrementally from 1 to 1000 and the results are
> dumped into a matrix. Then these matrices are put into a
> single cell. See below.
>
> for i = 1 : 1;
> A1(i,1) = B(i,1);
> end
>
> for i = 1 : 2; %increments of 1; i.e., 1,2,3,4...1000
> A2(i,1) = B(i,1);
> end
>
> for i = 1 : 1000; %last value
> A1000(i,1) = B(i,1);
> end
>
> wrap = {A1, A2, A3, A4, A5 ..., A1000}
> Obviously, you're not going to type it a 1000 times over.
> But can't find an easier way to do this. I've gotten this,
> but obviously it doesn't work:
> for i = 1 : 1000;
> A{i,1}(i,1) = B(i,1);
> end

I'm glad you recognize the cell array as the correct storage! The
simple coding solution is to use a second for loop

for j=1:1000
  for i=1:j
    A{j}(i) = B(i);
  end
end

But MATLAB matrix indexing is powerful:

for j=1:1000
  A{j} = B(1:j);
end

-Peter

Peter Boettcher <boettcher@ll.mit.edu> wrote in message
<muyhchubj1x.fsf@G99-Boettcher.llan.ll.mit.edu>...
> "mat lav" <mattylaver.delete.this.nospamy@gmail.com> writes:
>
> > The concept is really simple but I can't write the for-loop
> > that will do the job. In the for-loop, the upper limit
> > changes incrementally from 1 to 1000 and the results are
> > dumped into a matrix. Then these matrices are put into a
> > single cell. See below.
> >
> > for i = 1 : 1;
> > A1(i,1) = B(i,1);
> > end
> >
> > for i = 1 : 2; %increments of 1; i.e., 1,2,3,4...1000
> > A2(i,1) = B(i,1);
> > end
> >
> > for i = 1 : 1000; %last value
> > A1000(i,1) = B(i,1);
> > end
> >
> > wrap = {A1, A2, A3, A4, A5 ..., A1000}
> > Obviously, you're not going to type it a 1000 times over.
> > But can't find an easier way to do this. I've gotten this,
> > but obviously it doesn't work:
> > for i = 1 : 1000;
> > A{i,1}(i,1) = B(i,1);
> > end
>
> I'm glad you recognize the cell array as the correct
storage! The
> simple coding solution is to use a second for loop

The redundant sample code from my original post was just to
illustrate what I wanted to do - to lay out the concept. I
thought I was clear on that. There is no way anyone would
follow that approach. That's why I messed around with:
for i = 1 : 1000;
    A{i,1}(i,1) = B(i,1);
end
but couldn't get it work. It gave me the structure I wanted
- but with only point values (obviously).


>
> for j=1:1000
> for i=1:j
> A{j}(i) = B(i);
> end
> end
>
> But MATLAB matrix indexing is powerful:
>
> for j=1:1000
> A{j} = B(1:j);
> end
>
> -Peter

Yes, this method works. I didn't know about the matrix
indexing - I would never have guessed the name had you not
mentioned it for until now, from previous post, the syntax
B(1:j,1) looked like a typo.