[Numpy-discussion] arrays and : behaviour
did did
21did21 at gmx.com
Thu May 1 13:49:25 EDT 2014
thanks, it works well !!!!
see you and thanks again
----- Original Message -----
From: Sebastian Berg
Sent: 05/01/14 03:54 PM
To: numpy-discussion at scipy.org
Subject: Re: [Numpy-discussion] arrays and : behaviour
On Do, 2014-05-01 at 09:45 -0400, Benjamin Root wrote: > By default, the hold is already True. In fact, that might explain some > of the differences in what you are seeing. There are more points in > the second image than in the first one, so I wonder if you are seeing > some leftovers of previous plot commands? > > > One issue I do see is that the slicing is incorrect. [0:3] means index > 0, 1, and 2. So index 3 is never accessed. I think you want [0:4]. > > > I should also note that once you have your data as a numpy array, your > indexing can be greatly simplified: > plt.plot(array4D[0][0][0:4][0],array4D[0][0][0:4][0],'bo') > > can be done as: > plt.plot(array4D[0, 0, 0:4, 0], array4D[0, 0, 0:4, 0], 'bo') > Yeah, also arr[0:4][0] is the same as arr[0]. So you actually *must* use an array and the arr[0:4, 0] way if you want to do indexing like that... - Sebastian > > Cheers! > Ben Root > > > > On Thu, May 1, 2014 at 8:33 AM, Eelco Hoogendoorn > <hoogendoorn.eelco at gmail.com> wrote: > You problem isn't with colon indexing, but with the > interpretation of the arguments to plot. multiple calls to > plot with scalar arguments do not have the same result as a > single call with array arguments. For this to work as > intended, you would need plt.hold(True), for starters, and > maybe there are other subtleties. > > > On Thu, May 1, 2014 at 1:31 PM, did did <21did21 at gmx.com> > wrote: > > Hello all and sorry for my bad english, > > i am a beginner with python and i try to save a lot of > data in several folders in a 4D matrix > and then to plot two columns of this 4D matrix. > > Bellow, i have the code to fill my 4D matrix, it works > very well : > > [CODE]matrix4D=[] > for i in Numbers: > readInFolder=folderPrefixe+i+"/" > matrix3D=[] > for j in listeOfdata: > nameOfFile=filePrefixe+i+"-"+j+extensionTXT > nameOfFile=readInFolder+nameOfFile > > matrix2D=np.loadtxt(nameOfFile,delimiter=",",skiprows=1) > matrix3D.append(matrix2D) > matrix4D.append(matrix3D) > array4D = np.asarray(matrix4D)[/CODE] > > But now, i want to plot the third column as function > of the third too (just for trying) and i use > this stupid manner that works well : > > [CODE]plt.figure(1) > temp=plt.plot(array4D[0][0][0][0],array4D[0][0][0][0],'bo') > temp=plt.plot(array4D[0][0][1][0],array4D[0][0][1][0],'bo') > temp=plt.plot(array4D[0][0][2][0],array4D[0][0][2][0],'bo') > temp=plt.plot(array4D[0][0][3][0],array4D[0][0][3][0],'bo') > plt.show()[/CODE] > > Now, i want to use a more smart manner and i use ":" > like this > > [CODE]plt.figure(1) > temp=plt.plot(array4D[0][0][0:3][0],array4D[0][0][0:3][0],'bo') > plt.show()[/CODE] > > The result should be the same but i don't got the same > results!!! > > In attachement you have the two corresponding plots, > can you explain to me with > i don't have the same plots ?? > > thanks for all > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion at scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion > > > > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion at scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion > > > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion at scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion
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