numpy-discussion

Re: [Numpy-discussion] ValueError: object too deep for

[Kenny O. <kor...@id...>]

Yeah thanks guys, I printed them out the size and realized what it was doing 
then used a for loop to put it into the 1D array, but thanks Travis the way 
you said makes it easier than the for loop.

-Kenny 

[Numpy-discussion] complex numbers

[Kenny O. <kor...@id...>]

excuse my laziness for not looking this up, I googled it but could not find 
a solution.
matlab has a
isreal(array)
where if the array is full of real numbers the value returned is 1.
I'm translating matlab code and ran across

if ~isreal(array)
    array = abs(array)

Is there a way to check to see if a number is real or complex? and if so is 
there a way to extract the(a + ib) because the absolute value of a complex 
number is like the pythagorean therom on a and b?

thanks for your help,
Kenny

Re: [Numpy-discussion] complex numbers

[David L G. <Dav...@no...>]

PS:  The Python built in function (i.e., you don't even need numpy for 
this) abs(x) is "vectorized" (i.e., accepts a (nested) sequence, incl. 
numpy array, argument) and overloaded to give the modulus (i.e., 
Pythagorean "length") of a complex number when such is its argument.

DG

Kenny Ortmann wrote:
> excuse my laziness for not looking this up, I googled it but could not find 
> a solution.
> matlab has a
> isreal(array)
> where if the array is full of real numbers the value returned is 1.
> I'm translating matlab code and ran across
>
> if ~isreal(array)
>     array = abs(array)
>
> Is there a way to check to see if a number is real or complex? and if so is 
> there a way to extract the(a + ib) because the absolute value of a complex 
> number is like the pythagorean therom on a and b?
>
> thanks for your help,
> Kenny
>
>
>
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Re: [Numpy-discussion] complex numbers

[Tim H. <tim...@ie...>]

David L Goldsmith wrote:
> PS:  The Python built in function (i.e., you don't even need numpy for 
> this) abs(x) is "vectorized" (i.e., accepts a (nested) sequence, incl. 
> numpy array, argument) and overloaded to give the modulus (i.e., 
> Pythagorean "length") of a complex number when such is its argument.
>   
This isn't quite right. The built in abs function looks for the special 
method __abs__. So, abs(x) is equivalent to x.__abs__(). Arrays supply 
an appropriate __abs__ method, lists do not. For example:

 >>> l = [1,2,3,4]
 >>> abs(l)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: bad operand type for abs()
 >>> a = numpy.arange(5)
 >>> abs(a)
array([0, 1, 2, 3, 4])


-tim
> DG
>
> Kenny Ortmann wrote:
>   
>> excuse my laziness for not looking this up, I googled it but could not find 
>> a solution.
>> matlab has a
>> isreal(array)
>> where if the array is full of real numbers the value returned is 1.
>> I'm translating matlab code and ran across
>>
>> if ~isreal(array)
>>     array = abs(array)
>>
>> Is there a way to check to see if a number is real or complex? and if so is 
>> there a way to extract the(a + ib) because the absolute value of a complex 
>> number is like the pythagorean therom on a and b?
>>
>> thanks for your help,
>> Kenny
>>
>>
>>
>> -------------------------------------------------------------------------
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>> Join SourceForge.net's Techsay panel and you'll get the chance to share your
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>> https://lists.sourceforge.net/lists/listinfo/numpy-discussion
>>   
>>     
>
>
>   

Re: [Numpy-discussion] complex numbers

[Tim H. <tim...@ie...>]

Kenny Ortmann wrote:
> excuse my laziness for not looking this up, I googled it but could not find 
> a solution.
> matlab has a
> isreal(array)
> where if the array is full of real numbers the value returned is 1.
> I'm translating matlab code and ran across
>
> if ~isreal(array)
>     array = abs(array)
>
> Is there a way to check to see if a number is real or complex?
There may be a better way, but::

    alltrue(isreal(x))

Would work. As would:

    not sometrue(x.imag)

In the above test you are already negating the test, so you could just 
drop the not.
>  and if so is 
> there a way to extract the(a + ib) because the absolute value of a complex 
> number is like the pythagorean therom on a and b?
>   
I'm not entirely sure what you are looking for here, but x.imag and 
x.real will give you the real and imaginary parts. abs(x) will return 
the magnitude of x whether x is real or complex. x.conj() will return 
complex conjugate.

I'm somewhat suspicious of that matlab code. The code given is 
discontinuous as you cross the negative real axis. Does the result 
subsequently get squared or something? I'm guessing that either the 
matlab code is doing extra work, or there are some hidden assumptions 
(all values are in the positive real half-plane). Or some such. In 
either case, you'd probably be OK just skipping the check for realness 
and always taking the absolute of array. I can't say for sure without 
more context though.

-tim

Re: [Numpy-discussion] complex numbers

[David G. <Dav...@no...>]

numpy.isreal(a) is a "top level" function (i.e., not a class member 
function) in numpy; here's its help doc:

Help on function isreal in module numpy.lib.type_check:

isreal(x)
    Return a boolean array where elements are True if that element
    is real (has zero imaginary part)
   
    For scalars, return a boolean.

As for checking for pure imaginaries (i.e., real part == 0), one could use:

    x.imag == -j*x

or

    numpy.isreal(i*x)

or simply

    (x.real == 0.0) and (x.imag != 0.0)

DG

Kenny Ortmann wrote:
> excuse my laziness for not looking this up, I googled it but could not find 
> a solution.
> matlab has a
> isreal(array)
> where if the array is full of real numbers the value returned is 1.
> I'm translating matlab code and ran across
>
> if ~isreal(array)
>     array = abs(array)
>
> Is there a way to check to see if a number is real or complex? and if so is 
> there a way to extract the(a + ib) because the absolute value of a complex 
> number is like the pythagorean therom on a and b?
>
> thanks for your help,
> Kenny
>
>
>
> -------------------------------------------------------------------------
> Take Surveys. Earn Cash. Influence the Future of IT
> Join SourceForge.net's Techsay panel and you'll get the chance to share your
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Re: [Numpy-discussion] complex numbers

[David L G. <Dav...@no...>]

Thanks Tim,

DG

Tim Hochberg wrote:
> David L Goldsmith wrote:
>   
>> PS:  The Python built in function (i.e., you don't even need numpy for 
>> this) abs(x) is "vectorized" (i.e., accepts a (nested) sequence, incl. 
>> numpy array, argument) and overloaded to give the modulus (i.e., 
>> Pythagorean "length") of a complex number when such is its argument.
>>   
>>     
> This isn't quite right. The built in abs function looks for the special 
> method __abs__. So, abs(x) is equivalent to x.__abs__(). Arrays supply 
> an appropriate __abs__ method, lists do not. For example:
>
>  >>> l = [1,2,3,4]
>  >>> abs(l)
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> TypeError: bad operand type for abs()
>  >>> a = numpy.arange(5)
>  >>> abs(a)
> array([0, 1, 2, 3, 4])
>
>
> -tim
>   
>> DG
>>
>> Kenny Ortmann wrote:
>>   
>>     
>>> excuse my laziness for not looking this up, I googled it but could not find 
>>> a solution.
>>> matlab has a
>>> isreal(array)
>>> where if the array is full of real numbers the value returned is 1.
>>> I'm translating matlab code and ran across
>>>
>>> if ~isreal(array)
>>>     array = abs(array)
>>>
>>> Is there a way to check to see if a number is real or complex? and if so is 
>>> there a way to extract the(a + ib) because the absolute value of a complex 
>>> number is like the pythagorean therom on a and b?
>>>
>>> thanks for your help,
>>> Kenny
>>>
>>>
>>>
>>> -------------------------------------------------------------------------
>>> Take Surveys. Earn Cash. Influence the Future of IT
>>> Join SourceForge.net's Techsay panel and you'll get the chance to share your
>>> opinions on IT & business topics through brief surveys -- and earn cash
>>> http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
>>> _______________________________________________
>>> Numpy-discussion mailing list
>>> Num...@li...
>>> https://lists.sourceforge.net/lists/listinfo/numpy-discussion
>>>   
>>>     
>>>       
>>   
>>     
>
>
>
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