Hi All,
I have an 2D numeric array of x,y points eg [(1,3),(2,4),(5,6)] and I would like to remove all the points in the array that don't meet the min/max
criteria. I will have several thousand points. With lists I can do it
Thanks to Tim and Chris. Just what I was looking for! I tested both along with some other tries that I had made. For 10000 points  G:\GPS\Python\GUI_Test\Filter>speed.py time for <function listComp at 0x007AE4D8> is 0.022809 time for <function arraykludge at 0x0092AFF0> is 0.060303 time for <function arrayComp at 0x0092AFB0> is 0.055692 time for <function arrayTimH at 0x0092B030> is 0.003652 time for <function arrayChrisB at 0x0092B070> is 0.003561 For 100 points  G:\GPS\Python\GUI_Test\Filter>speed.py time for <function listComp at 0x007AE4D8> is 0.000238 time for <function arraykludge at 0x00804BD8> is 0.000784 time for <function arrayComp at 0x00804B98> is 0.000678 time for <function arrayTimH at 0x00804C18> is 0.000376 time for <function arrayChrisB at 0x00804C58> is 0.000153 They scale slightly differently between Tim's and Chris' methods. Thanks again, Gordon Williams Here is the code (since someone will ask): '''Test the speed of different methods of getting points out of a list''' import time import Numeric as n size= 100 maxNum=size/10. #data a= n.array(n.arange(0,maxNum,.05)) a.shape= (size,2) #list l= a.tolist() (xMin,yMin)= (3,2) (xMax,yMax)= (4,6) def listComp(seq): '''using list comprehension''' return [(x,y) for x,y in seq if xMin < x <xMax and yMin< y <yMax] def arrayComp(seq): '''using list comprehension''' return n.array([(x,y) for x,y in seq if xMin < x <xMax and yMin< y <yMax]) def arraykludge(seq): '''using numeric stuff''' res= n.copy.deepcopy(seq) i=0 #index for x,y in seq: if xMin < x <xMax and yMin< y <yMax: res[i]= [x,y] i+=1 return res[:i] def arrayTimH(seq): '''using Tim Hochberg suggestions''' cond = (xMin < seq[:,0]) & (seq[:,0] < xMax) & (yMin < seq[:,1]) & (seq[:,1] < yMax) return n.compress(cond, seq, 0) def arrayChrisB(seq): '''using Chris Barker suggestions''' valid = (seq[:,0] > xMin) & (seq[:,0] < xMax) & (seq[:,1] > yMin) & (seq[:,1] < yMax) return n.take(a,n.nonzero(valid)) #Tests tests= [(listComp,l), (arraykludge,a),(arrayComp,a), (arrayTimH,a), (arrayChrisB,a)] for fun,seq in tests: t=time.clock() apply(fun,(seq,)) dt= time.clock()t print "time for %s is %f" %(str(fun),dt)  Original Message  From: "Gordon Williams" <g_will@cyberus.ca> To: <numpydiscussion@lists.sourceforge.net> Sent: Thursday, February 27, 2003 2:05 PM Subject: filtering numeric arrays point like
[(x,y) for x,y in seq if xMin < x <xMax and yMin< y <yMax]
How do I get the same functionality and better speed using numeric. I
have
tried a bunch of things using compress and take but I am running up against a brick wall.
Any ideas?
Thanks
Gordon Williams
participants (1)

Gordon Williams