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--- other:python:misc_by_jyp [2022/02/21 12:47]
jypeter [Sorting] Added link to numpy routines
+++ other:python:misc_by_jyp [2022/02/21 15:15]
jypeter [numpy related stuff]
@@ Line 221: / Line 221: @@
 ['c', 'd', 'b', 'a']</code>
+==== numpy related stuff ====
+=== Finding and counting unique values ===
+Use ''np.unique'', do **not** try to use histogram related functions!
+<code>>>> vals = np.random.randint(2, 5, (10,)) * 0.5 # Get 10 discreet float values
+>>> vals
+array([1. , 2. , 1. , 2. , 2. , 1.5, 1. , 1.5, 2. , 1.5])
+>>> np.unique(vals)
+array([1. , 1.5, 2. ])
+>>> unique_vals, nb_unique = np.unique(vals, return_counts=True)
+>>> unique_vals
+array([1. , 1.5, 2. ])
+>>> nb_unique
+array([3, 3, 4])
+>>> sorted_vals = np.sort(vals) # Sorted copy, in order to check the result
+>>> sorted_vals
+array([1. , 1. , 1. , 1.5, 1.5, 1.5, 2. , 2. , 2. , 2. ])</code>
+=== Applying a ufunc over all the elements of an array ===
+There are all sorts of //ufuncs// (Universal Functions), and we will just use below ''add'' from the [[https://numpy.org/doc/stable/reference/ufuncs.html#math-operations|math operations]], applied on the arrays defined in [[#finding_and_counting_unique_values|Finding and counting unique values]]
+<code># Get the sum of all the elements of 'vals'
+>>> np.add.reduce(vals)
+.5
+>>> np.add.reduce(sorted_vals)
+.5
+>>> vals.sum() # The usual and easy way to do it
+.5</code>
 /*

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