`Acos`#

Description#

Inverse cosine of each element. Output is in the range \([0, \pi]\) when the input is in \([-1, 1]\).

Equation:

\[ y[i] = \arccos(x[i]) \]

Parameters: Acos takes no parameters.

NaN handling: Inputs outside \([-1, 1]\) produce NaN. Existing NaN values pass through.

NaN handling#

Policy: ignore. A NaN in any input at index t causes the function to skip that step: output at t is NaN and internal state is unchanged. Subsequent finite samples are processed as if step t had not occurred.

Examples#

Usage example#

import numpy as np
import plotly.graph_objects as go
from plotly.subplots import make_subplots
from screamer import Acos

np.random.seed(0)
data = np.clip(np.random.normal(size=80) * 0.6, -1.0, 1.0)
transformed = Acos()(data)

fig = make_subplots(rows=2, cols=1, shared_xaxes=True,
                    row_heights=[0.5, 0.5], vertical_spacing=0.1)
fig.add_trace(go.Scatter(y=data, mode="lines+markers",
                         name="input"), row=1, col=1)
fig.add_trace(go.Scatter(y=transformed, mode="lines+markers",
                         name="Acos",
                         line=dict(color="red")), row=2, col=1)
fig.update_layout(
    title="Acos transformation",
    margin=dict(l=20, r=20, t=60, b=20),
    legend=dict(orientation="h", yanchor="bottom", y=1.02,
                xanchor="right", x=1),
)
fig.update_yaxes(title_text="input (clipped to [-1, 1])", row=1, col=1)
fig.update_yaxes(title_text="Acos(input)", row=2, col=1)
fig.show()

Reference#

Equivalent to numpy.arccos.

Acos#