extending arrays

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extending arrays

Dave Comer-2
Can anyone tell me the Octave quivalen of the following (valid)
Matlab statement:

dydx = [ 1, dydx ];

dydx is a 120 x 1 element array. The idea is to add one element to
the array. When I execute this in octave I get the following:

octave:29> size(dydx)
ans =

  120    1

octave:30> dydx = [1, dydx];
error: number of rows must match near line 30, column 12
error: evaluating assignment expression near line 30, column 6

Thanks,

Dave Comer

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extending arrays

John W. Eaton-6
On 28-Feb-1997, Dave Comer <[hidden email]> wrote:

| Can anyone tell me the Octave quivalen of the following (valid)
| Matlab statement:
|
| dydx = [ 1, dydx ];
|
| dydx is a 120 x 1 element array. The idea is to add one element to
| the array. When I execute this in octave I get the following:
|
| octave:29> size(dydx)
| ans =
|
|   120    1
|
| octave:30> dydx = [1, dydx];
| error: number of rows must match near line 30, column 12
| error: evaluating assignment expression near line 30, column 6

Are you sure this is valid in MATLAB?  With 4.2c, I get:

  >> a = [1;2]

  a =

       1
       2

  >> [0,a]
  ???  All matrices on a row in the bracketed expression must have the
   same number of rows.

  >> [0;a]

  ans =

       0
       1
       2

This also works for Octave.

jwe

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Re: extending arrays

Dave Comer-2
John W. Eaton wrote:

>
> On 28-Feb-1997, Dave Comer <[hidden email]> wrote:
>
> | Can anyone tell me the Octave quivalen of the following (valid)
> | Matlab statement:
> |
> | dydx = [ 1, dydx ];
> |
> | dydx is a 120 x 1 element array. The idea is to add one element to
> | the array. When I execute this in octave I get the following:
> |
> | octave:29> size(dydx)
> | ans =
> |
> |   120    1
> |
> | octave:30> dydx = [1, dydx];
> | error: number of rows must match near line 30, column 12
> | error: evaluating assignment expression near line 30, column 6
>
> Are you sure this is valid in MATLAB?

No, I'm not. I'm reading through "MATLAB for Engineers" by
Biran and Breiner, where the following statement is made (p.44):

"To plot dydx together with y we must add an element; it is dy/dx
calculated at the point x=0, that is d(sin x)/dx at x=0. Type

>>dydx = [ 1, dydx ];"

I'm not sure if the authors are using MATLAB 3.5 or 4.0 as both
are mentioned in the into and no definitive statement is made.
The version isn't relavent, as I can see from your answer. Must be
a mis-print.


Thanks for setting me straight John!

Dave


>  With 4.2c, I get:
>
>   >> a = [1;2]
>
>   a =
>
>        1
>        2
>
>   >> [0,a]
>   ???  All matrices on a row in the bracketed expression must have the
>    same number of rows.
>
>   >> [0;a]
>
>   ans =
>
>        0
>        1
>        2
>
> This also works for Octave.
>
> jwe

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