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Added challenge to 01-numpy.md regarding slicing a vector vs an array #211

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Jun 21, 2016
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Added challenge to 01-numpy.md regarding slicing a vector vs an array #211

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Added challenge to 01-numpy.md regarding
metavee Jan 21, 2016
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Reworked proposed challenge on slicing vectors.
metavee Jun 17, 2016
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19 changes: 19 additions & 0 deletions 01-numpy.md
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Expand Up @@ -703,3 +703,22 @@ the graphs will actually be squeezed together more closely.)
> ## Moving plots around {.challenge}
>
> Modify the program to display the three plots on top of one another instead of side by side.

> ## Converting between an array and a vector {.challenge}
>
> In some cases in NumPy, an vector of size N behaves differently than an Nx1 array.
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I don't think this challenge really explains how it might behave differently, or why that might even be a problem?

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Fair point. In my experience, it generally results in strange-looking broadcasting errors.

Perhaps I could reformat this as a small code fragment that results in such an error, and the challenge would be to fix the error. Do you think that would work better?

> The vector will have a shape (N,), while the array will have a shape (N,1).
>
> The code below generates a 5x5 array of random numbers `A`,
> then uses slices to extract the last column of `A` as a vector with shape (5,) and store it in `b`.
>
> Modify it so that `b` is an array with shape (5,1).
>
> ~~~ {.python}
> import numpy
>
> A = numpy.random.random([5,5]) # array of random numbers
> b = A[:,-1] # take the last column from A
>
> print(b.shape)
> ~~~