How do you use `tickmode=sync` and how can you align `y=0`

[FLudwig]

I have two questions about graphs with two y-axes:

• How do you use tickmode = "sync"? (There’s an example below where I’m doing something wrong - I don’t know what…)
• How can I align the zero-line so that y = 0 is at the same position for both axes? (In the example below I’m trying out a few different options, none of them work.)

from typing import Any

import plotly.graph_objects as go


def sample_fig_y_align() -> dict[str, go.Figure]:
    """Fuction to try out different combinations of y-axis properties.

    Returns:
        - dict[str, go.Figure]: Dictionary of figures
    """

    # sample data
    y_axis_1: dict[str, Any] = {
        "name": "first y-axis",
        "y_values": [200, 8, 0, 250, 110],
        "y_axis": "y",
        "fill": "tozeroy",
    }
    y_axis_2: dict[str, Any] = {
        "name": "second y-axis",
        "y_values": [-3, -1, 4, -2, 2],
        "y_axis": "y2",
        "fill": "tozeroy",
    }

    # base fig with no special changes in layout
    fig_base: go.Figure = go.Figure()
    for trace in [y_axis_1, y_axis_2]:
        fig_base.add_trace(
            go.Scatter(
                name=trace["name"],
                y=trace["y_values"],
                yaxis=trace["y_axis"],
                fill=trace["fill"],
            )
        )
    fig_base.update_layout(
        {
            "title": {"text": "Base"},
            "legend": {"orientation": "h"},
            "yaxis2": {
                "side": "right",
                "overlaying": "y",
                "tickmode": "sync",
            },
        }
    )
    fig_base.show()

    # layout changes to try and align y = 0
    tests_y2: dict[str, dict[str, Any]] = {
        "from post": {  # https://community.plotly.com/t/align-multiple-y-axis-to-one-value-in-plotly/44500
            "rangemode": "tozero",
            "scaleanchor": "y",
            "scaleratio": 1,
            "constraintoward": "bottom",
        },
        "config_1": {
            "scaleanchor": "y",
            "constrain": "domain",
            "constraintoward": "bottom",
        },
        "config_2": {
            "scaleanchor": "y",
            "constrain": "range",
            "constraintoward": "bottom",
        },
        "config_3": {
            "anchor": "x",
        },
        "config_4": {
            "matches": "y",
            "autorange": True,
        },
    }

    figs: dict[str, go.Figure] = {
        test_key: go.Figure(
            fig_base.update_layout(
                {
                    "title": {"text": str(test_dict)},
                    "yaxis2": test_dict,
                }
            )
        )
        for (test_key, test_dict) in list(tests_y2.items())
    }

    for test_fig in figs:
        figs[test_fig].show()

    return figs

…this is how the base graph looks like for me - notice that the ticks aren’t synced and y = 0 are in different positions:

[AIMPED]

Hi, does this help?

Align Multiple Y axis to one value in Plotly

I have the following code (slightly modified from Plotly’s page) import plotly.graph_objects as go from plotly.subplots import make_subplots # Create figure with secondary y-axis fig = make_subplots(specs=[[{"secondary_y": True}]]) # Add traces fig.add_trace( go.Scatter(x=[1, 2, 3], y=[40, 50, 60], name="yaxis data"), secondary_y=False, ) fig.add_trace( go.Scatter(x=[2, 3, 4], y=[80, 40, 30], name="yaxis2 data"), secondary_y=True, ) # Add figure title fig.update_layout( …

[FLudwig]

Hi @AIMPED ,

thanks for your reply. I’ve seen this post - it’s the first test in my code (see the dictionary tests_y2). Unfortunately it doesn’t help. If you look at my data, the y-values in y_axis_1 include a zero and the y-values in y_axis_2 are positive and negative. As I understand it, rangemode='tozero' does nothing in this case, since both include zero anyway…

Also my question about tickmode = "sync" doesn’t get addressed in this topic as that option didn’t exist when that topic was created.