[EMAIL PROTECTED] wrote: >Hi, > >I have recieved the following note from a user: > >""" >In SciPy 0.3.x the ufuncs were overloaded by more "intelligent" versions. >A very attractive feature was that sqrt(-1) would yield 1j as in Matlab. >Then you can program formulas directly (e.g., roots of a 2nd order >polynomial) and the right answer is always achieved. In the Matlab-Python >battle in mathematics education, this feature is important. > >Now in SciPy 0.5.x sqrt(-1) yields nan. A lot of code we have, especially >for introductory numerics and physics courses, is now broken. >This has already made my colleagues at the University skeptical to >Python as "this lack of backward compatibility would never happen in Matlab". > > This was a consequence of moving scipy_base into NumPy but not exposing the scimath library in NumPy. It would be a very easy thing to put from numpy.lib.scimath import * into the scipy name-space.
I'm supportive of that as a backward-compatibility measure. >Another problem related to Numeric and numpy is that in these courses we >use ScientificPython several places, which applies Numeric and will >continue to do so. You then easily get a mix of numpy and Numeric >in scripts, which may cause problems and at least extra overhead. >Just converting to numpy in your own scripts isn't enough if you call >up libraries using and returning Numeric. > > >""" > >I wonder, what are the reasons that numpy.sqrt(-1) returns nan? > > Because that is backwards compatible. You have to construct a function-wrapper in order to handle the negative case correctly. The function wrapper is going to be slower. Thus, it is placed in a separate library. >Could sqrt(-1) made to return 1j again? > Not in NumPy. But, in scipy it could. >If not, shouldn't > > >numpy.sqrt(-1) raise a ValueError instead of returning silently nan? > > This is user adjustable. You change the error mode to raise on 'invalid' instead of pass silently which is now the default. -Travis ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Numpy-discussion mailing list Numpy-discussion@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/numpy-discussion
