Re: Differences between Octave and Matlab on division (/) operator with scalar and vector

[James Sherman Jr.]

On Sat, Mar 25, 2017 at 2:51 PM, Juan Pablo Carbajal
<address@hidden> wrote:
> On Sat, Mar 25, 2017 at 6:48 PM, José Luis García Pallero
> <address@hidden> wrote:
>> Hello:
>>
>> Using this variables:
>>
>> a = 2;
>> b = [1 2 3];
>>
>> For the operation a/b or 2/b or b/2 I obtain an error in Octave and
>> Matlab due to wrong dimensions. But if I declare b as a vector column
>> as b=[1 2 3]' I obtain in Octave:
>>
>>>> a/b
>> ans =
>>
>>    0.14286   0.28571   0.42857
>>
>> and in Matlab:
>>
>>>> a/b
>>
>> ans =
>>
>>          0         0    0.6667
>>
>> What is the reason of this difference? Why the operation is legal with
>> b as column vector and illegal with row vector?
>>
>> Thanks
>>
>> --
>> *****************************************
>> José Luis García Pallero
>> address@hidden
>> (o<
>> / / \
>> V_/_
>> Use Debian GNU/Linux and enjoy!
>> *****************************************
>>
>> _______________________________________________
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>> address@hidden
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> In Octave a/b when b is a matrix (any size), is equivalent to
> a*inv(b), in this case a*pinv(b) (try it out).
> I can't see what matlab is doing, but the last element is 2/3.
>
> I also do not understand why there is an error in the first case,
> should given the same result...i.e. apply a*pinv(b) when b is a row
> vector
>
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> address@hidden
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I just tried this on MATLAB version 2016a, and got the following results:

>> a = 2;
>> b = [1 2 3];
>> 2/b
Error using  /
Matrix dimensions must agree.
>> a/b
Error using  /
Matrix dimensions must agree.
>> b/2
ans =
    0.5000    1.0000    1.5000

Are you sure that b/2 caused an error?  That is well defined and
should produce elementwise division by 2.

James Sherman