# [Numpy-discussion] arrays and : behaviour

Eelco Hoogendoorn hoogendoorn.eelco at gmail.com
Thu May 1 08:33:52 EDT 2014

```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:
>     matrix3D=[]
>     for j in listeOfdata:
>         nameOfFile=filePrefixe+i+"-"+j+extensionTXT
>         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
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>
>
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