# Source code for mars.tensor.arithmetic.arctan

```
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright 1999-2020 Alibaba Group Holding Ltd.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import numpy as np
from ... import opcodes as OperandDef
from ..utils import infer_dtype
from .core import TensorUnaryOp
from .utils import arithmetic_operand
@arithmetic_operand(sparse_mode='unary')
class TensorArctan(TensorUnaryOp):
_op_type_ = OperandDef.ARCTAN
_func_name = 'arctan'
[docs]@infer_dtype(np.arctan)
def arctan(x, out=None, where=None, **kwargs):
"""
Trigonometric inverse tangent, element-wise.
The inverse of tan, so that if ``y = tan(x)`` then ``x = arctan(y)``.
Parameters
----------
x : array_like
out : Tensor, None, or tuple of Tensor and None, optional
A location into which the result is stored. If provided, it must have
a shape that the inputs broadcast to. If not provided or `None`,
a freshly-allocated tensor is returned. A tuple (possible only as a
keyword argument) must have length equal to the number of outputs.
where : array_like, optional
Values of True indicate to calculate the ufunc at that position, values
of False indicate to leave the value in the output alone.
**kwargs
Returns
-------
out : Tensor
Out has the same shape as `x`. Its real part is in
``[-pi/2, pi/2]`` (``arctan(+/-inf)`` returns ``+/-pi/2``).
It is a scalar if `x` is a scalar.
See Also
--------
arctan2 : The "four quadrant" arctan of the angle formed by (`x`, `y`)
and the positive `x`-axis.
angle : Argument of complex values.
Notes
-----
`arctan` is a multi-valued function: for each `x` there are infinitely
many numbers `z` such that tan(`z`) = `x`. The convention is to return
the angle `z` whose real part lies in [-pi/2, pi/2].
For real-valued input data types, `arctan` always returns real output.
For each value that cannot be expressed as a real number or infinity,
it yields ``nan`` and sets the `invalid` floating point error flag.
For complex-valued input, `arctan` is a complex analytic function that
has [`1j, infj`] and [`-1j, -infj`] as branch cuts, and is continuous
from the left on the former and from the right on the latter.
The inverse tangent is also known as `atan` or tan^{-1}.
References
----------
Abramowitz, M. and Stegun, I. A., *Handbook of Mathematical Functions*,
10th printing, New York: Dover, 1964, pp. 79.
http://www.math.sfu.ca/~cbm/aands/
Examples
--------
We expect the arctan of 0 to be 0, and of 1 to be pi/4:
>>> import mars.tensor as mt
>>> mt.arctan([0, 1]).execute()
array([ 0. , 0.78539816])
>>> mt.pi/4
0.78539816339744828
Plot arctan:
>>> import matplotlib.pyplot as plt
>>> x = mt.linspace(-10, 10)
>>> plt.plot(x.execute(), mt.arctan(x).execute())
>>> plt.axis('tight')
>>> plt.show()
"""
op = TensorArctan(**kwargs)
return op(x, out=out, where=where)
```