Re: [Tutor] finding a maximum between the absolute difference of several columns
Andre' Walker-Loud wrote: import numpy as np Vhel_fdiff3 = np.array([abs(Vmatch3_1 - Vmatch3_2), abs(Vmatch3_1 - Vmatch3_3), abs(Vmatch3_3 - Vmatch3_2)]) your_answer = Vhel_fdiff3.max(axis=0) or import numpy as np a = np.array([Vmatch3_1-Vmatch3_2, Vmatch3_1-Vmatch3_3, Vmatch3_3- Vmatch3_2]) print np.max(np.abs(a), axis=0) ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] finding a maximum between the absolute difference of several columns
import numpy as np Vhel_fdiff3 = np.array([abs(Vmatch3_1 - Vmatch3_2), abs(Vmatch3_1 - Vmatch3_3), abs(Vmatch3_3 - Vmatch3_2)]) your_answer = Vhel_fdiff3.max(axis=0) or import numpy as np a = np.array([Vmatch3_1-Vmatch3_2, Vmatch3_1-Vmatch3_3, Vmatch3_3- Vmatch3_2]) print np.max(np.abs(a), axis=0) yes, this one is better than mine. It is more flexible, leaving more options for what you may want to do with it afterwards, andre ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] finding a maximum between the absolute difference of several columns
Hello all, I am still scripting away and have reached my next quandry, this one is much simpler than the last, basically I read in a file with several columns. Vmatch3_1=dat[col1] Vmatch3_2=dat[col2] Vmatch3_3=dat[col3] Vdav=5.0 Vhel_fdiff3=max(abs(Vmatch3_1 - Vmatch3_2),abs(Vmatch3_1 - Vmatch3_3),abs(Vmatch3_3 - Vmatch3_2)) What I would like this to return is the maximum difference in each case, so I end up with one column which contains only the largest differences. now I use this to write the condition: with_v1_3=(Vhel_fdiff3 = Vdav) I know the condition works and plots if Vhel_fdiff3=(Vmatch3_1 - Vmatch3_2) for example, and I know this syntax would work if it was numbers instead of columns. max(abs(1-2),abs(3-7),abs(2-4)) 4 The error is: --- Traceback (most recent call last): File double_plot.py, line 109, in module Vhel_fdiff3=max(abs(Vmatch3_1 - Vmatch3_2),abs(Vmatch3_1 - Vmatch3_3),abs(Vmatch3_3 - Vmatch3_2)) ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() - So it can't handle the fact that it's columns of numbers and not single numbers, so my question is, can I solve this without doing a loop around it... use numpy, or some other function instead? I've been searching around and haven't found any good ways forward so I thought one of you might know. Thanks ~Elaina -- PhD Candidate Department of Physics and Astronomy Faculty of Science Macquarie University North Ryde, NSW 2109, Australia ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] finding a maximum between the absolute difference of several columns
On 17/02/2012 01:04, Elaina Ann Hyde wrote: Hello all, I am still scripting away and have reached my next quandry, this one is much simpler than the last, basically I read in a file with several columns. Vmatch3_1=dat[col1] Vmatch3_2=dat[col2] Vmatch3_3=dat[col3] Vdav=5.0 Vhel_fdiff3=max(abs(Vmatch3_1 - Vmatch3_2),abs(Vmatch3_1 - Vmatch3_3),abs(Vmatch3_3 - Vmatch3_2)) What I would like this to return is the maximum difference in each case, so I end up with one column which contains only the largest differences. now I use this to write the condition: with_v1_3=(Vhel_fdiff3= Vdav) I know the condition works and plots if Vhel_fdiff3=(Vmatch3_1 - Vmatch3_2) for example, and I know this syntax would work if it was numbers instead of columns. max(abs(1-2),abs(3-7),abs(2-4)) 4 The error is: --- Traceback (most recent call last): File double_plot.py, line 109, inmodule Vhel_fdiff3=max(abs(Vmatch3_1 - Vmatch3_2),abs(Vmatch3_1 - Vmatch3_3),abs(Vmatch3_3 - Vmatch3_2)) ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() - So it can't handle the fact that it's columns of numbers and not single numbers, so my question is, can I solve this without doing a loop around it... use numpy, or some other function instead? I've been searching around and haven't found any good ways forward so I thought one of you might know. Thanks ~Elaina ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor Throwing the error message into google gave a pile of hits from stackoverflow.com, which indicate that the error message is from numpy. See if this can get you going http://stackoverflow.com/questions/1322380/gotchas-where-numpy-differs-from-straight-python. The fourth answer down states this is a horrible problem so I'll duck out here, sorry :) -- Cheers. Mark Lawrence. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] finding a maximum between the absolute difference of several columns
On Fri, Feb 17, 2012 at 1:41 PM, Rohan Sachdeva rsach...@usc.edu wrote: The way I would do this is to put all of the differences in a list then take the maximum of the list. So.. a = Vmatch3_1 - Vmatch3_2 b = Vmatch3_1 - Vmatch3_3 c = Vmatch3_3 - Vmatch3_2 Vhel_fdiff3=max([a,b,c]) That should work. a,b,c are pretty bad variable names... Rohan On Thu, Feb 16, 2012 at 5:04 PM, Elaina Ann Hyde elainah...@gmail.comwrote: Hello all, I am still scripting away and have reached my next quandry, this one is much simpler than the last, basically I read in a file with several columns. Vmatch3_1=dat[col1] Vmatch3_2=dat[col2] Vmatch3_3=dat[col3] Vdav=5.0 Vhel_fdiff3=max(abs(Vmatch3_1 - Vmatch3_2),abs(Vmatch3_1 - Vmatch3_3),abs(Vmatch3_3 - Vmatch3_2)) What I would like this to return is the maximum difference in each case, so I end up with one column which contains only the largest differences. now I use this to write the condition: with_v1_3=(Vhel_fdiff3 = Vdav) I know the condition works and plots if Vhel_fdiff3=(Vmatch3_1 - Vmatch3_2) for example, and I know this syntax would work if it was numbers instead of columns. max(abs(1-2),abs(3-7),abs(2-4)) 4 The error is: --- Traceback (most recent call last): File double_plot.py, line 109, in module Vhel_fdiff3=max(abs(Vmatch3_1 - Vmatch3_2),abs(Vmatch3_1 - Vmatch3_3),abs(Vmatch3_3 - Vmatch3_2)) ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() - So it can't handle the fact that it's columns of numbers and not single numbers, so my question is, can I solve this without doing a loop around it... use numpy, or some other function instead? I've been searching around and haven't found any good ways forward so I thought one of you might know. Thanks ~Elaina -- PhD Candidate Department of Physics and Astronomy Faculty of Science Macquarie University North Ryde, NSW 2109, Australia ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor -- Thanks for the replies so far. I don't think that Rohan's idea solves the numbers versus columns issue. If I run it I get --- Traceback (most recent call last): File double_plot.py, line 112, in module Vhel_fdiff3=max(a,b,c) ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() - which is just the same error, I looked at the forums and the link suggested and I guess maybe my problem is trickier than I first thought! ~Elaina -- PhD Candidate Department of Physics and Astronomy Faculty of Science Macquarie University North Ryde, NSW 2109, Australia ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] finding a maximum between the absolute difference of several columns
On 17/02/2012 02:53, Elaina Ann Hyde wrote: On Fri, Feb 17, 2012 at 1:41 PM, Rohan Sachdevarsach...@usc.edu wrote: The way I would do this is to put all of the differences in a list then take the maximum of the list. So.. a = Vmatch3_1 - Vmatch3_2 b = Vmatch3_1 - Vmatch3_3 c = Vmatch3_3 - Vmatch3_2 Vhel_fdiff3=max([a,b,c]) That should work. a,b,c are pretty bad variable names... Rohan On Thu, Feb 16, 2012 at 5:04 PM, Elaina Ann Hydeelainah...@gmail.comwrote: Hello all, I am still scripting away and have reached my next quandry, this one is much simpler than the last, basically I read in a file with several columns. Vmatch3_1=dat[col1] Vmatch3_2=dat[col2] Vmatch3_3=dat[col3] Vdav=5.0 Vhel_fdiff3=max(abs(Vmatch3_1 - Vmatch3_2),abs(Vmatch3_1 - Vmatch3_3),abs(Vmatch3_3 - Vmatch3_2)) What I would like this to return is the maximum difference in each case, so I end up with one column which contains only the largest differences. now I use this to write the condition: with_v1_3=(Vhel_fdiff3= Vdav) I know the condition works and plots if Vhel_fdiff3=(Vmatch3_1 - Vmatch3_2) for example, and I know this syntax would work if it was numbers instead of columns. max(abs(1-2),abs(3-7),abs(2-4)) 4 The error is: --- Traceback (most recent call last): File double_plot.py, line 109, inmodule Vhel_fdiff3=max(abs(Vmatch3_1 - Vmatch3_2),abs(Vmatch3_1 - Vmatch3_3),abs(Vmatch3_3 - Vmatch3_2)) ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() - So it can't handle the fact that it's columns of numbers and not single numbers, so my question is, can I solve this without doing a loop around it... use numpy, or some other function instead? I've been searching around and haven't found any good ways forward so I thought one of you might know. Thanks ~Elaina -- PhD Candidate Department of Physics and Astronomy Faculty of Science Macquarie University North Ryde, NSW 2109, Australia ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor -- Thanks for the replies so far. I don't think that Rohan's idea solves the numbers versus columns issue. If I run it I get --- Traceback (most recent call last): File double_plot.py, line 112, inmodule Vhel_fdiff3=max(a,b,c) ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() - which is just the same error, I looked at the forums and the link suggested and I guess maybe my problem is trickier than I first thought! ~Elaina ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor I've found this http://comments.gmane.org/gmane.comp.python.tutor/72882. HTH. -- Cheers. Mark Lawrence. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] finding a maximum between the absolute difference of several columns
On Fri, Feb 17, 2012 at 2:27 PM, Mark Lawrence breamore...@yahoo.co.ukwrote: On 17/02/2012 02:53, Elaina Ann Hyde wrote: On Fri, Feb 17, 2012 at 1:41 PM, Rohan Sachdevarsach...@usc.edu wrote: The way I would do this is to put all of the differences in a list then take the maximum of the list. So.. a = Vmatch3_1 - Vmatch3_2 b = Vmatch3_1 - Vmatch3_3 c = Vmatch3_3 - Vmatch3_2 Vhel_fdiff3=max([a,b,c]) That should work. a,b,c are pretty bad variable names... Rohan On Thu, Feb 16, 2012 at 5:04 PM, Elaina Ann Hydeelainah...@gmail.com** wrote: Hello all, I am still scripting away and have reached my next quandry, this one is much simpler than the last, basically I read in a file with several columns. Vmatch3_1=dat[col1] Vmatch3_2=dat[col2] Vmatch3_3=dat[col3] Vdav=5.0 Vhel_fdiff3=max(abs(Vmatch3_1 - Vmatch3_2),abs(Vmatch3_1 - Vmatch3_3),abs(Vmatch3_3 - Vmatch3_2)) What I would like this to return is the maximum difference in each case, so I end up with one column which contains only the largest differences. now I use this to write the condition: with_v1_3=(Vhel_fdiff3= Vdav) I know the condition works and plots if Vhel_fdiff3=(Vmatch3_1 - Vmatch3_2) for example, and I know this syntax would work if it was numbers instead of columns. max(abs(1-2),abs(3-7),abs(2-4)**) 4 The error is: --- Traceback (most recent call last): File double_plot.py, line 109, inmodule Vhel_fdiff3=max(abs(Vmatch3_1 - Vmatch3_2),abs(Vmatch3_1 - Vmatch3_3),abs(Vmatch3_3 - Vmatch3_2)) ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() - So it can't handle the fact that it's columns of numbers and not single numbers, so my question is, can I solve this without doing a loop around it... use numpy, or some other function instead? I've been searching around and haven't found any good ways forward so I thought one of you might know. Thanks ~Elaina -- PhD Candidate Department of Physics and Astronomy Faculty of Science Macquarie University North Ryde, NSW 2109, Australia __**_ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/**mailman/listinfo/tutorhttp://mail.python.org/mailman/listinfo/tutor -- Thanks for the replies so far. I don't think that Rohan's idea solves the numbers versus columns issue. If I run it I get --- Traceback (most recent call last): File double_plot.py, line 112, inmodule Vhel_fdiff3=max(a,b,c) ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() - which is just the same error, I looked at the forums and the link suggested and I guess maybe my problem is trickier than I first thought! ~Elaina __**_ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/**mailman/listinfo/tutorhttp://mail.python.org/mailman/listinfo/tutor I've found this http://comments.gmane.org/**gmane.comp.python.tutor/72882http://comments.gmane.org/gmane.comp.python.tutor/72882 . HTH. -- Cheers. Mark Lawrence. __**_ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/**mailman/listinfo/tutorhttp://mail.python.org/mailman/listinfo/tutor Interesting, thanks for all the ideas everyone I did finally get it to work in a loop form. Anyone wanting to save themselves lots of confusion, firstly use .append, and secondly don't forget to convert created lists back to arrays for numpy, here is the working code to look through columns, match them, return and make an array to operate on with numpy: - Vhel_fdiff3=[] for i in xrange(len(Vmatch3_1)): Vhel_fdiff3.append(max([abs(Vmatch3_1[i] - Vmatch3_2[i]),abs(Vmatch3_1[i] - Vmatch3_3[i]),abs(Vmatch3_3[i] - Vmatch3_2[i])])) #print Vhel_fdiff3 #appending writes a list, but numpy which makes the with_ work needs an array Vhel_fdiff3=array(Vhel_fdiff3) - ~Elaina -- PhD Candidate Department of Physics and Astronomy Faculty of Science Macquarie University North Ryde, NSW 2109, Australia ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] finding a maximum between the absolute difference of several columns
Hi Elaina, Vhel_fdiff3=[] for i in xrange(len(Vmatch3_1)): Vhel_fdiff3.append(max([abs(Vmatch3_1[i] - Vmatch3_2[i]),abs(Vmatch3_1[i] - Vmatch3_3[i]),abs(Vmatch3_3[i] - Vmatch3_2[i])])) #print Vhel_fdiff3 #appending writes a list, but numpy which makes the with_ work needs an array Vhel_fdiff3=array(Vhel_fdiff3) You can skip making the list and directly make a numpy array. import numpy as np ... Vhel_fdiff3 = np.zeros_like(Vmatch3_1) for i in xrange(len(Vmatch3_1): Vhel_fdiff3[i] = max(abs(Vmatch3_1[i] - Vmatch3_2[i]),abs(Vmatch3_1[i] - Vmatch3_3[i]),abs(Vmatch3_3[i] - Vmatch3_2[i])) But, more importantly, you can do it all in numpy - have a read about the max function http://scipy.org/Numpy_Example_List#head-7918c09eea00e59ec399064e7d5e1e672d242f60 Given an 2-dimensional array, you can find the max for each row or each column by specifying which axis you want to compare against. Almost surely, the built in numpy function will be faster than your loop - even if you precompile it by importing your functions in another file. You can do something like import numpy as np Vhel_fdiff3 = np.array([abs(Vmatch3_1 - Vmatch3_2), abs(Vmatch3_1 - Vmatch3_3), abs(Vmatch3_3 - Vmatch3_2)]) #create an array of the absolute values of the differences of each pair of data # Vhel_fdiff3 is a 2D array # the first index runs over the three pairs of differences # the second index runs over the elements of each pair # to get the maximum difference, you want to compare over the first axis (0) your_answer = Vhel_fdiff3.max(axis=0) but you may not want the abs value of the differences, but to actually keep the differences, depending on which one has the maximum abs difference - that would require a little more coding. Andre ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
