Where

Description

Where is a conditional element-wise selector over three aligned input streams. Given inputs mask, a, and b:

• output is a when mask is nonzero (any nonzero value counts as true)

• output is b when mask is zero

If mask is NaN, the output is NaN. If the selected branch (a when mask is nonzero, b when zero) is NaN, that NaN passes through as the output.

Parameters: Where takes no parameters.

Examples

Usage example

import numpy as np
import plotly.graph_objects as go
from plotly.subplots import make_subplots
from screamer import Where, GreaterEqual

np.random.seed(0)
a = np.cumsum(np.random.normal(size=200))
b = np.cumsum(np.random.normal(size=200))
cond = GreaterEqual()(a, b)             # 1.0 where a >= b, else 0.0
out = Where()(cond, a, b)               # pick a where cond is nonzero, else b

fig = make_subplots(rows=2, cols=1, shared_xaxes=True,
                    row_heights=[0.55, 0.45], vertical_spacing=0.08)
fig.add_trace(go.Scatter(y=a, mode="lines", name="a"), row=1, col=1)
fig.add_trace(go.Scatter(y=b, mode="lines", name="b"), row=1, col=1)
fig.add_trace(go.Scatter(y=out, mode="lines", name="a if a >= b else b",
                         line=dict(color="red")), row=2, col=1)
fig.update_layout(title="Pick the larger of two signals (Where)",
                  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="inputs", row=1, col=1)
fig.update_yaxes(title_text="selected", row=2, col=1)
fig.show()