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2. python - What does -1 mean in numpy reshape? - Stack Overflow

   stackoverflow.com/questions/18691084

   This answer contains a lot of examples but doesn't lay out what -1 does in plain English. When reshaping an array, the new shape must contain the same number of elements as the old shape, meaning the products of the two shapes' dimensions must be equal.

3. What does [:, :] mean on NumPy arrays - Stack Overflow

   stackoverflow.com/questions/16815928

   numpy uses tuples as indexes. In this case, this is a detailed slice assignment. [0] #means line 0 of your matrix [(0,0)] #means cell at 0,0 of your matrix [0:1] #means lines 0 to 1 excluded of your matrix [:1] #excluding the first value means all lines until line 1 excluded [1:] #excluding the last param mean all lines starting form line 1 included [:] #excluding both means all lines [::2] # ...

4. python - Is there a NumPy function to return the first index of...

   stackoverflow.com/questions/432112

   For maximum performance use index_of__v5 (numba + numpy.enumerate + for loop; see the code below). If numba is not available: Use index_of__v7 (for loop + enumerate) if the target value is expected to be found within the first 100k elements. Else use index_of__v2/v3/v4 (numpy.argmax or numpy.flatnonzero based). Powered by perfplot

5. difference between np.inf and float ('Inf') - Stack Overflow

   stackoverflow.com/questions/42315541

   np.inf (6 chars) math.inf (8 chars; new in python 3.5) float ('inf') (12 chars) That means if you already have NumPy imported you can save yourself 6 (or 2) chars per occurrence compared to float ('inf') (or math.inf). Because it's easier to remember. At least for me, it's far easier to remember np.inf than that I need to call float with a string.

6. How do I check which version of NumPy I'm using?

   stackoverflow.com/questions/1520234

   1. This is actually very nice as it allows you to check the version of numpy even if you have two different versions running on two different versions of python. py -2 -c "import numpy; print (numpy.version.version)" py -3 -c "import numpy; print (numpy.version.version)" – JSWilson.

7. Difference between numpy.array shape (R, 1) and (R,)

   stackoverflow.com/questions/22053050

   In numpy, some of the operations return in shape (R, 1) but some return (R,). This will make matrix multiplication more tedious since explicit reshape is required. For example, given a matrix M, if we want to do numpy.dot(M[:,0], numpy.ones((1, R))) where R is the number of rows

8. python - How can I upgrade NumPy? - Stack Overflow

   stackoverflow.com/questions/28517937

   RuntimeError: module compiled against API version 9 but this version of numpy is 6 Traceback (most recent call last): File "<string>", line 1, in <module> ImportError: numpy.core.multiarray failed to import I tried to upgrade NumPy, but this is confusing: >>> import numpy >>> print numpy.__version__ 1.6.1

9. In numpy, what does selection by [:,None] do? - Stack Overflow

   stackoverflow.com/questions/37867354

   3. If you see code from experienced NumPy users, you will often see them use a special slicing syntax instead of calling reshape. x = v[None, :] or. x = v[:, None] Those lines create a slice that looks at all of the items of v but asks NumPy to add a new dimension of size 1 for the associated axis.

10. Error "Import Error: No module named numpy" on Windows

    stackoverflow.com/questions/7818811

    pip3 install numpy" results in "Requirement already satisfied: numpy in c:\users\peter\appdata\local\programs\python\python36-32\lib\site-packages". You'd expect python's "import numpy" would be able to find it, but no. ModuleNotFoundError: No module named 'numpy' So this answer may work in some narrow context, but not in general.

11. How do I remove NaN values from a NumPy array? - Stack Overflow

    stackoverflow.com/questions/11620914

    609. To remove NaN values from a NumPy array x: x = x[~numpy.isnan(x)] Explanation. The inner function numpy.isnan returns a boolean/logical array which has the value True everywhere that x is not-a-number. Since we want the opposite, we use the logical-not operator ~ to get an array with True s everywhere that x is a valid number.