Hello, If it is not running as you want it, you should say what went wrong. Post the code that you have tried and the expected output, please. (In fact, the lack of expected output was the reason why my suggestion was completely off target.) Rui Barradas On 07/08/2018 09:20, Maija Sirkj?rvi wrote:> Thanks, but I didn't quite get it. And I don't get it running as it should. > > ti 7. elok. 2018 klo 10.47 Martin Maechler (maechler at stat.math.ethz.ch > <mailto:maechler at stat.math.ethz.ch>) kirjoitti: > > > > Thanks for help! > > However, changing the index from i to j for the column vector > changes the > > output. I would like the matrix to be the following: > > > -1 1 0 0 0 0 0 > > 0 -1 1 0 0 0 0 > > 0 0 -1 1 0 0 0 > > ..... > > etc. > > > How to code it? > > as Enrico Schumann showed you: Without any loop, a very nice > R-ish way (see his message)! > > Martin > > > Best, > > Maija >
Thanks!
If I do it like this:
myMatrix <- matrix(0,5,5*2-3)
print(myMatrix)
for(i in 2:nrow(myMatrix))
for(j in 2:ncol(myMatrix))
myMatrix[i-1,j-1] = -1
myMatrix[i-1,j] = 1
print(myMatrix)
I get the following result:
[,1] [,2] [,3] [,4] [,5] [,6] [,7]
[1,] -1 -1 -1 -1 -1 -1 0
[2,] -1 -1 -1 -1 -1 -1 0
[3,] -1 -1 -1 -1 -1 -1 0
[4,] -1 -1 -1 -1 -1 -1 1
[5,] 0 0 0 0 0 0 0
However. The result that I would need to get would be like this:
[,1] [,2] [,3] [,4] [,5] [,6] [,7]
[1,] -1 1 0 0 0 0 0
[2,] 0 -1 1 0 0 0 0
[3,] 0 0 -1 1 0 0 0
[4,] 0 0 0 -1 1 0 0
[5,] 0 0 0 0 -1 1 0
I'd rather not create symmetric matrices as I would really like to learn
how to do this thing "the hard way" as I find matrix iteration to be
quite
a basic procedure in everything I'm trying to do.
Thanks again!
Maija
ti 7. elok. 2018 klo 17.37 Rui Barradas (ruipbarradas at sapo.pt) kirjoitti:
> Hello,
>
> If it is not running as you want it, you should say what went wrong.
> Post the code that you have tried and the expected output, please.
> (In fact, the lack of expected output was the reason why my suggestion
> was completely off target.)
>
> Rui Barradas
>
> On 07/08/2018 09:20, Maija Sirkj?rvi wrote:
> > Thanks, but I didn't quite get it. And I don't get it running
as it
> should.
> >
> > ti 7. elok. 2018 klo 10.47 Martin Maechler (maechler at
stat.math.ethz.ch
> > <mailto:maechler at stat.math.ethz.ch>) kirjoitti:
> >
> >
> > > Thanks for help!
> > > However, changing the index from i to j for the column
vector
> > changes the
> > > output. I would like the matrix to be the following:
> >
> > > -1 1 0 0 0 0 0
> > > 0 -1 1 0 0 0 0
> > > 0 0 -1 1 0 0 0
> > > .....
> > > etc.
> >
> > > How to code it?
> >
> > as Enrico Schumann showed you: Without any loop, a very nice
> > R-ish way (see his message)!
> >
> > Martin
> >
> > > Best,
> > > Maija
> >
>
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You only need one "for loop"
for(i in 2:nrow(myMatrix)) {
myMatrix[i-1,i-1] = -1
myMatrix[i-1,i] = 1
}
HTH,
Eric
On Wed, Aug 8, 2018 at 12:40 PM, Maija Sirkj?rvi <maija.sirkjarvi at
gmail.com>
wrote:
> Thanks!
>
> If I do it like this:
>
> myMatrix <- matrix(0,5,5*2-3)
> print(myMatrix)
> for(i in 2:nrow(myMatrix))
> for(j in 2:ncol(myMatrix))
> myMatrix[i-1,j-1] = -1
> myMatrix[i-1,j] = 1
> print(myMatrix)
>
> I get the following result:
>
> [,1] [,2] [,3] [,4] [,5] [,6] [,7]
> [1,] -1 -1 -1 -1 -1 -1 0
> [2,] -1 -1 -1 -1 -1 -1 0
> [3,] -1 -1 -1 -1 -1 -1 0
> [4,] -1 -1 -1 -1 -1 -1 1
> [5,] 0 0 0 0 0 0 0
>
> However. The result that I would need to get would be like this:
>
> [,1] [,2] [,3] [,4] [,5] [,6] [,7]
> [1,] -1 1 0 0 0 0 0
> [2,] 0 -1 1 0 0 0 0
> [3,] 0 0 -1 1 0 0 0
> [4,] 0 0 0 -1 1 0 0
> [5,] 0 0 0 0 -1 1 0
>
> I'd rather not create symmetric matrices as I would really like to
learn
> how to do this thing "the hard way" as I find matrix iteration to
be quite
> a basic procedure in everything I'm trying to do.
>
> Thanks again!
> Maija
>
>
>
>
> ti 7. elok. 2018 klo 17.37 Rui Barradas (ruipbarradas at sapo.pt)
kirjoitti:
>
> > Hello,
> >
> > If it is not running as you want it, you should say what went wrong.
> > Post the code that you have tried and the expected output, please.
> > (In fact, the lack of expected output was the reason why my suggestion
> > was completely off target.)
> >
> > Rui Barradas
> >
> > On 07/08/2018 09:20, Maija Sirkj?rvi wrote:
> > > Thanks, but I didn't quite get it. And I don't get it
running as it
> > should.
> > >
> > > ti 7. elok. 2018 klo 10.47 Martin Maechler (maechler at
stat.math.ethz.ch
> > > <mailto:maechler at stat.math.ethz.ch>) kirjoitti:
> > >
> > >
> > > > Thanks for help!
> > > > However, changing the index from i to j for the column
vector
> > > changes the
> > > > output. I would like the matrix to be the following:
> > >
> > > > -1 1 0 0 0 0 0
> > > > 0 -1 1 0 0 0 0
> > > > 0 0 -1 1 0 0 0
> > > > .....
> > > > etc.
> > >
> > > > How to code it?
> > >
> > > as Enrico Schumann showed you: Without any loop, a very nice
> > > R-ish way (see his message)!
> > >
> > > Martin
> > >
> > > > Best,
> > > > Maija
> > >
> >
>
> [[alternative HTML version deleted]]
>
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>
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