Went ahead and added an enhancement request: http://projects.scipy.org/scipy/numpy/ticket/293
This is something I've wanted in the past too. --bb On 9/25/06, Charles R Harris <[EMAIL PROTECTED]> wrote: > > > On 9/24/06, Bill Baxter <[EMAIL PROTECTED]> wrote: > > Howdy Angus, > > Yeh, that does seem like a hole in the API. Travis added a rollaxis() > > but there's still no simple way to roll the elements themselves. > > > > I took a look at numpy.fft.fftshift, which is a function that has to > > do a similar thing. It does it by concatenating aranges and then > > doing a take(). Presumably Pearu knew what he was doing when he wrote > > that, so we can assume this is probably close to the best possible. > > :-) From that idea here's a function that implements roll(). > > > > def roll(y,shift,axis): > > """Roll the elements in the array by 'shift' positions along the > > given axis.""" > > from numpy import asanyarray,concatenate,arange > > y = asanyarray(y) > > n = y.shape[axis] > > shift %= n # does the right thing for negative shifts, too > > return > y.take(concatenate((arange(shift,n),arange(shift))), axis) > > It is possible to do a shift inplace using two reflections implemented with > swaps. This works because two reflections is the same as a rotating twice > the distance between the centers of the reflections. I don't know if it is > worth implementing this, however. > > Chuck ------------------------------------------------------------------------- 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 Numpy-discussion@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/numpy-discussion
