Re: why no arg, abs methods for comlex type?
Daniel Schüle wrote: [...] Derive your own subclass of complex and define those methods. I think something as basic as an angle/arg of complex number definetly belongs to the interface, and it would not even require a great effort to put it there shrug Okay. Write a patch. Personally, I would prefer that it be a function in cmath rather than a method because then it could be made to work on integers and regular floats, too. most complex formulas out there use Euler representation it's a waste of code lines (and programmers time) to write 3 liner functions for the transformion between a+bj - (r,angle) It's a very, very tiny outlay of effort on the programmer's part that only has to happen once in their career. Python makes things covenient so we have complex numbers in the core language the calculations where perfectly possible without them using (re, im) tupels and many many sin/cos in the code but imagine how ugly it would be .. I don't have to imagine. It's not all that ugly. I would like see Python as a competitor to Matlab etc I think it is already. -- Robert Kern [EMAIL PROTECTED] In the fields of hell where the grass grows high Are the graves of dreams allowed to die. -- Richard Harter -- http://mail.python.org/mailman/listinfo/python-list
Re: why no arg, abs methods for comlex type?
[...] shrug Okay. Write a patch. Personally, I would prefer that it be a function in cmath rather than a method because then it could be made to work on integers and regular floats, too. Ok, but what semantic should angle/arg have, say for 3 respectively for 3.0? the same as for arg(3+0j)? -- http://mail.python.org/mailman/listinfo/python-list
Re: why no arg, abs methods for comlex type?
Daniel Schüle wrote: shrug Okay. Write a patch. Personally, I would prefer that it be a function in cmath rather than a method because then it could be made to work on integers and regular floats, too. Ok, but what semantic should angle/arg have, say for 3 respectively for 3.0? the same as for arg(3+0j)? As a potential user, that's what I would expect. See Dan Bishop's implementation (earlier in this thread). -- http://mail.python.org/mailman/listinfo/python-list
Re: why no arg, abs methods for comlex type?
On Sat, 06 Aug 2005 06:44:03 GMT, Dennis Lee Bieber [EMAIL PROTECTED] wrote: On Fri, 05 Aug 2005 18:24:26 +0200, Daniel Schüle [EMAIL PROTECTED] declaimed the following in comp.lang.python: c = 1+1j c.arg(angle_mode = cmath.GRAD) - 45.0 Is that right? The result looks more like Degrees... maybe I confuse, in german one would say 45 Grad I took a freedom to translate it directly :) well, my calculator shows a D which most likely stands for Degree, I cannot tell for sure 45 Degrees = 50 Grad 2PI = 360 Degree = 400 Grad (and military protractors are the only place I've seen Grads used) No one seems to have mentioned 2PI = 1 circle as in unit circles. IIRC, back in the day before math chips, we implemented all the trig functions in terms of angles where some number of bits respresented one circle, for best resolution of angles with a given number of bits. Also for compatibility with angular input devices. Also for the natural modulo 2PI effect of representing an angle as an int, with unsigned interval [0..2PI) or signed interval [-PI..PI). IIRC, FFTs involve phase in steps of 2PI/2**n also (for power-of-2 decimation effectively dividing the unit circle in terms of powers of e**-i*(2*pi/2**n)) (where i is imaginary 0+1j). Hm, let' see, for 45-degree deltas (2PI/2**3) ... import cmath (cmath.e+0j)**(-2j*cmath.pi/2**3) (0.70710678118654757-0.70710678118654746j) for c in [((cmath.e+0j)**(-2j*cmath.pi/2**3))**i for i in xrange(8)]: print c ... (1+0j) (0.707106781187-0.707106781187j) (1.5701957963e-016-1j) (-0.707106781187-0.707106781187j) (-1-3.1403915926e-016j) (-0.707106781187+0.707106781187j) (-4.71058738891e-016+1j) (0.707106781187+0.707106781187j) Regards, Bengt Richter -- http://mail.python.org/mailman/listinfo/python-list
why no arg, abs methods for comlex type?
Hello all, I often have to deal with complex numbers using python iteractive as calculator I wonder why there are no methods like arg, abs well one can use c = 1+1j abs(c) In my opinion it would also be nice to have the possibility to write it as c.abs() it looks more OO unfortunately there is no arg method to get the angle of the complex number of course it easy to write one on your own (that's what I have done for myself) but differnt people will create and reinvite the wheel over and over again while reading alien code one will have to spend 2 seconds remembering the function names etc consider c = 1+1j c.arg(angle_mode = cmath.GRAD) - 45.0 or c.arg(angle_mode = cmath.RAD) - 0.7853.. I would also like to see some more functions to make calculations with complex number more convenient e.g. c = 27 c.pow(numerator = 1, denominator = 3, mode = cmath.EULER, angle_mode = cmath.GRAD) - ((3,0), (3,120), (3,240)) what do you think about it? maybe there exists some proposals aiming this goal? -- Daniel -- http://mail.python.org/mailman/listinfo/python-list
Re: why no arg, abs methods for comlex type?
I would also like to see some more functions to make calculations with complex number more convenient e.g. c = 27 c = 27+0j -- http://mail.python.org/mailman/listinfo/python-list
Re: why no arg, abs methods for comlex type?
Daniel Schüle [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] I wonder why there are no methods like arg, abs well one can use c = 1+1j abs(c) In my opinion it would also be nice to have the possibility to write it as c.abs() it looks more OO Python is object based but not rigidly OO in syntax or looks. This is an intentional design decision. Not being gratuitiously redundant is another. unfortunately there is no arg method to get the angle of the complex number I agree that this is a deficiency. I would think .angle() should be a no-param method like .conjugate(), though its internal implementation would need access to the appropriate cmath functions. I think returning radians might be enough though. You could submit to the SourceForge tracker a RFE (Request For Enhancement) if not a patch. I would also like to see some more functions to make calculations with complex number more convenient e.g. c = 27 c.pow(numerator = 1, denominator = 3, mode = cmath.EULER, angle_mode = cmath.GRAD) - ((3,0), (3,120), (3,240)) Wanting all roots is fairly specialized. sqrt(4) is 2, not (2, -2). what do you think about it? maybe there exists some proposals aiming this goal? Have you looked for complex math functions in numpy, numarray, scipy or similar packages? It is possible that a cmath2 module, written in Python, could be useful. Terry J. Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: why no arg, abs methods for comlex type?
On Fri, 05 Aug 2005 15:42:41 +0200, Daniel Schüle [EMAIL PROTECTED] wrote: Hello all, I often have to deal with complex numbers using python iteractive as calculator I wonder why there are no methods like arg, abs well one can use c = 1+1j abs(c) In my opinion it would also be nice to have the possibility to write it as c.abs() it looks more OO I guess it's for the same reason that we are spared from writing things like this: z = x.squared().added_to(y.squared()).squareroot() E = m.multiplied_by(c.squared()) More OO, yes. More readable, not IMO. I would also like to see some more functions to make calculations with complex number more convenient [ ... ] maybe there exists some proposals aiming this goal? SciPy or Numeric? Regards, Dan -- Dan Sommers http://www.tombstonezero.net/dan/ -- http://mail.python.org/mailman/listinfo/python-list
Re: why no arg, abs methods for comlex type?
Terry Reedy wrote: Daniel Schüle [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] ... unfortunately there is no arg method to get the angle of the complex number I agree that this is a deficiency. I would think .angle() should be a no-param method like .conjugate(), though its internal implementation would need access to the appropriate cmath functions. You need math, not cmath. def arg(z): The Argument of z, in radians. z += 0j # make it work on real inputs return math.atan2(z.imag, z.real) -- http://mail.python.org/mailman/listinfo/python-list
Re: why no arg, abs methods for comlex type?
Hi Terry, In my opinion it would also be nice to have the possibility to write it as c.abs() it looks more OO Python is object based but not rigidly OO in syntax or looks. This is an intentional design decision. Not being gratuitiously redundant is another. I agree, redundancy confuses people unfortunately there is no arg method to get the angle of the complex number I agree that this is a deficiency. I would think .angle() should be a no-param method like .conjugate(), though its internal implementation would need access to the appropriate cmath functions. I think returning radians might be enough though. I don't know what nomenclature is used in english speaking mathematical world for angle of a complex number I learned it in german as Arg(z) .. Arg standing for argument you see, we would have named it differently, hence making it difficult for the reader, eventually creating redundancy You could submit to the SourceForge tracker a RFE (Request For Enhancement) if not a patch. I never did, but I will see c = 1 + 1j def arg(c, angle_mode = RAD): ... if angle_mode not in (RAD, GRAD): ... raise ValueError ... import math ... ret = math.atan2(c.imag, c.real) ... if angle_mode == GRAD: ... return ret / math.pi * 180 ... return ret it's pretty easy and straightforward implementation while writing this, I was struck by an idea and reimplemented it as following def arg(self, angle_mode = RAD): ... if angle_mode not in (RAD, GRAD): ... raise ValueError ... import math ... ret = math.atan2(self.imag, self.real) ... if angle_mode == GRAD: ... return ret / math.pi * 180 ... return ret ... class Complex(complex): pass Complex.arg = arg c = Complex(1+1j) c.arg(angle_mode = GRAD) 45.0 later I realized that this represents yet another implementation which could be done by someone, thus again leading to possible redundancy and confuse people all this would not have happened when we would have arg or angle builtin in complex type I would also like to see some more functions to make calculations with complex number more convenient e.g. c = 27 c.pow(numerator = 1, denominator = 3, mode = cmath.EULER, angle_mode = cmath.GRAD) - ((3,0), (3,120), (3,240)) Wanting all roots is fairly specialized. sqrt(4) is 2, not (2, -2). it could be named .allroots(n) - ((), (), ()) with n whole number indeed .pow() is not a good name for it, since z**x always yields one complex number if x is 2.5 or alike, it could be aproximated with n/m and use res = [] for i in z.allroots(m): res.append(i**n) I am not sure, this is correct iterpretation of z**2.5 I will need to ask in math newsgroup :) and approximation might not be good enough Have you looked for complex math functions in numpy, numarray, scipy or similar packages? It is possible that a cmath2 module, written in Python, could be useful. I hope so I will google for cmath2, I never heard about it I am new to Numeric and numarray, I was playing with them and ufunc-tionsand matplotlab, as for SciPy I couldnt find any binary for 2.4 Python unfortunately :-/ Regards -- Daniel -- http://mail.python.org/mailman/listinfo/python-list
Re: why no arg, abs methods for comlex type?
c = 1+1j c.arg(angle_mode = cmath.GRAD) - 45.0 Is that right? The result looks more like Degrees... maybe I confuse, in german one would say 45 Grad I took a freedom to translate it directly :) well, my calculator shows a D which most likely stands for Degree, I cannot tell for sure -- Daniel -- http://mail.python.org/mailman/listinfo/python-list
Re: why no arg, abs methods for comlex type?
Daniel Schüle wrote: what do you think about it? maybe there exists some proposals aiming this goal? Derive your own subclass of complex and define those methods. -- Erik Max Francis [EMAIL PROTECTED] http://www.alcyone.com/max/ San Jose, CA, USA 37 20 N 121 53 W AIM erikmaxfrancis I am not afraid / To be a lone Bohemian -- Lamya -- http://mail.python.org/mailman/listinfo/python-list
Re: why no arg, abs methods for comlex type?
Daniel Schüle wrote: maybe I confuse, in german one would say 45 Grad I took a freedom to translate it directly :) well, my calculator shows a D which most likely stands for Degree, I cannot tell for sure Probably. In English, you have degrees and gradians, which aren't the same thing; gradians are defined so that there are 400 gradians in a circle (so 100 gradians in a right angle). -- Erik Max Francis [EMAIL PROTECTED] http://www.alcyone.com/max/ San Jose, CA, USA 37 20 N 121 53 W AIM erikmaxfrancis I am not afraid / To be a lone Bohemian -- Lamya -- http://mail.python.org/mailman/listinfo/python-list
Re: why no arg, abs methods for comlex type?
Erik Max Francis wrote: Daniel Schüle wrote: maybe I confuse, in german one would say 45 Grad I took a freedom to translate it directly :) well, my calculator shows a D which most likely stands for Degree, I cannot tell for sure Probably. In English, you have degrees and gradians, which aren't the same thing; gradians are defined so that there are 400 gradians in a circle (so 100 gradians in a right angle). In German, they're Altgrad (degrees) and Neugrad or Gon (gradians). Reinhold -- http://mail.python.org/mailman/listinfo/python-list
Re: why no arg, abs methods for comlex type?
Daniel Schüle [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] I agree that this is a deficiency. I would think .angle() should be a I don't know what nomenclature is used in english speaking mathematical world for angle of a complex number I learned it in german as Arg(z) .. Arg standing for argument you see, we would have named it differently, hence making it difficult for the reader, eventually creating redundancy I am aware of the usage of argument to mean the angle in polar representation, but I don't like it. The word argument already has two other meanings, one in common English, the other in math/CS. The latter meaning is the inputs to a function, and that is how the word is used in Python (though the former applies more to many c.l.p threads ;-) To me, the polar angle has no connection with either meaning and so the usage is 'like Greek' to me. Whereas angle is exactly what it is. As for Greek: I first learned r(adius),theta (versus x,y or real,imag) as the names for polar coordinates or the polar representation for complex numbers and only ran into arg much later in some contexts. And I have seen complex number implementations that use the equivalent of c.r() and c.theta(). But I did not suggest that for one of the reasons I don't like 'lambda': its fine if you already know it and arbitrary if you don't. (Is theta used in Germany?) It is possible that a cmath2 module, written in Python, could be useful. I hope so I will google for cmath2, I never heard about it That is because we have not written it yet. The allroots function could be the first addition, if it is not present elsewhere. The 'could be' was meant in the sense of 'if someone were to write it' rather than 'if you were to read it' ;-) Terry J. Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: why no arg, abs methods for comlex type?
[...] I am aware of the usage of argument to mean the angle in polar representation, but I don't like it. The word argument already has two other meanings, one in common English, the other in math/CS. The latter meaning is the inputs to a function, and that is how the word is used in Python (though the former applies more to many c.l.p threads ;-) To me, the polar angle has no connection with either meaning and so the usage is 'like Greek' to me. Whereas angle is exactly what it is. .angle() would be also alright, as it is easy to grasp As for Greek: I first learned r(adius),theta (versus x,y or real,imag) as the names for polar coordinates or the polar representation for complex numbers and only ran into arg much later in some contexts. And I have seen complex number implementations that use the equivalent of c.r() and c.theta(). But I did not suggest that for one of the reasons I don't like 'lambda': its fine if you already know it and arbitrary if you don't. (Is theta used in Germany?) yes, of course the entire mathematic is full of them :) as for the complex numbers, in our lessons we used R(adius) and Phi for the angle for polar representation I guess it's more a question of teacher's preference than a national norm -- http://mail.python.org/mailman/listinfo/python-list
