df = pd.DataFrame({"x_val": np.arange(20)}).assign(
    y_val=lambda df: df["x_val"] * df["x_val"],
    noise=np.random.normal(scale=5, size=20),
)

d = {
    "vconcat": [
        {
            "input": "menu",
            "label": 'yCol',
            "options": [
                {"label": "Pure signal", "value": {"sql": "y_val"}},
                {"label": "Small noise", "value": {"sql": "y_val+noise"}},
                {"label": "Medium noise", "value": {"sql": "y_val+2*noise"}},
                {"label": "Large noise", "value": {"sql": "y_val+5*noise"}},
            ],
            "as": "$yCol",
        },
        {
            "plot": [
                {"mark": "lineY", "x": "x_val", "y": {"sql": "$yCol"}, "data": {"from": "df"}}
            ],
        },
    ],
}


MosaicWidget(d, data={'df': df})