# Matrix indexing a column on TI-89

• 07-17-2008, 09:48 PM
unix
Matrix indexing a column on TI-89
Hi:

A TI-89 question, but I don't know where else to ask (well there are
probably forums, but I'm old school USENET).

How to access a column of a matrix?

The dumb thing can of course access a row, as in:

[[1,2,3][4,5,6]][1] Enter

[1,2,3]

But how can I index one of the 3 columns in this matrix to get for ex,
the first column vector:

[[1][4]] ???

I suppose I will have to write a function for this. Just hoping there
is a built-in syntax for this.

Thanks.

--
Good day!

____________________________________
CRC
[email]crobcREMOVETHIS@BOGUSsbcglobal.net[/email]
NOTE, delete texts: "REMOVETHIS" and
• 07-18-2008, 02:24 PM
unix
Re: Matrix indexing a column on TI-89
On Jul 17, 5:48*pm, Chris Carlen <crobcREMOVET...@sbcglobal.net>
wrote:[color=blue]
> Hi:
>
> A TI-89 question, but I don't know where else to ask (well there are
> probably forums, but I'm old school USENET).
>
> How to access a column of a matrix?
>
> The dumb thing can of course access a row, as in:
>
> [[1,2,3][4,5,6]][1] Enter
>
> [1,2,3]
>
> But how can I index one of the 3 columns in this matrix to get for ex,
> the first column vector:
>
> [[1][4]] ???
>[/color]

Good question.
I do't tink there is a built in function for that,
but defining one is easy. Obviously, one can use the row access with
two transpositions to get the desired result.

Or I just tested "define col(m,n)=subMat(m,1,n,rowDim(m),n)", which
gives [1;3] for col([1,2;3,4],1) and [2;4] for col([1,2;3,4],2).
I also tested it with non-square matrices, just to be sure I did not
get the function arguments wrong, but they worked too.

• 07-23-2008, 09:45 PM
unix
Re: Matrix indexing a column on TI-89
> On Jul 17, 5:48 pm, Chris Carlen <crobcREMOVET...@sbcglobal.net>
> wrote:[color=green]
>> Hi:
>>
>> A TI-89 question, but I don't know where else to ask (well there are
>> probably forums, but I'm old school USENET).
>>
>> How to access a column of a matrix?
>>
>> The dumb thing can of course access a row, as in:
>>
>> [[1,2,3][4,5,6]][1] Enter
>>
>> [1,2,3]
>>
>> But how can I index one of the 3 columns in this matrix to get for ex,
>> the first column vector:
>>
>> [[1][4]] ???
>>[/color]
>
> Good question.
> I do't tink there is a built in function for that,
> but defining one is easy. Obviously, one can use the row access with
> two transpositions to get the desired result.
>
> Or I just tested "define col(m,n)=subMat(m,1,n,rowDim(m),n)", which
> gives [1;3] for col([1,2;3,4],1) and [2;4] for col([1,2;3,4],2).
> I also tested it with non-square matrices, just to be sure I did not
> get the function arguments wrong, but they worked too.[/color]

Thanks for the reply! I'll give that a whirl.

--
Good day!

____________________________________
CRC
[email]crobcREMOVETHIS@BOGUSsbcglobal.net[/email]
NOTE, delete texts: "REMOVETHIS" and