89 lines
2 KiB
Markdown
89 lines
2 KiB
Markdown
# Convert other data into numpy arrays e.g. asarray
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{:.no_toc}
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<nav markdown="1" class="toc-class">
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* TOC
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{:toc}
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</nav>
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## The goal
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Questions to [David Rotermund](mailto:davrot@uni-bremen.de)
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## [numpy.asarray](https://numpy.org/doc/stable/reference/generated/numpy.asarray.html)
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```python
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numpy.asarray(a, dtype=None, order=None, *, like=None)
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```
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The importance of **asarray**:
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> Convert the input to an array.
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```python
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import numpy as np
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a_list = [[1, 2], [3, 4]]
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a_np = np.asarray(a_list)
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w = np.asarray(1)
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print(w.sum()) # -> 1
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print(a_np.sum()) # -> 10
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print(a_np > 2)
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print(1.sum()) # SyntaxError: invalid decimal literal
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print(a_list.sum()) # AttributeError: 'list' object has no attribute 'sum'
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print(a_list > 2) # TypeError: '>' not supported between instances of 'list' and 'int'
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```
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Output:
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```python
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[[False False]
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[ True True]]
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```
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## [numpy.fromiter](https://numpy.org/doc/stable/reference/generated/numpy.fromiter.html)
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{: .topic-optional}
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This is an optional topic!
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```python
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numpy.fromiter(iter, dtype, count=-1, *, like=None)
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```
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> Create a new 1-dimensional array from an iterable object.
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## [numpy.fromfunction](https://numpy.org/doc/stable/reference/generated/numpy.fromfunction.html)
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{: .topic-optional}
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This is an optional topic!
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```python
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numpy.fromfunction(function, shape, *, dtype=<class 'float'>, like=None, **kwargs)[source]
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```
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> Construct an array by executing a function over each coordinate.
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>
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> The resulting array therefore has a value fn(x, y, z) at coordinate (x, y, z).
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## [numpy.array](https://numpy.org/doc/stable/reference/generated/numpy.array.html)
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{: .topic-optional}
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This is an optional topic!
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Don't confuse **asarray** with **array**. **array** can be used to put a numpy structure around data. **asarray** converts the data into a numpy array. (As far as I understand...). Thus normally you don't need to touch **array**.
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```python
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numpy.array(object, dtype=None, *, copy=True, order='K', subok=False, ndmin=0, like=None)
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```
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> Create an array.
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