plotly python change y-axis values ​to your own

Question

A graph of random values ​​is plotted. It is necessary to change the values ​​of the Y axis to others.

xg = np.random.rand(100, 1200)
fig = px.imshow(xg, aspect="auto",color_continuous_scale='ice')
fig.show()

values ​​to be changed

y1=np.arange(100)*0.5
y2=np.arange(100)*5

Thanks!

Answer 1

• 100 ticks on the yaxis is too many! Have gone with 10
• simple case of defining where you want ticks in the range of values (100) and text you want to display again domain value https://plotly.com/python/tick-formatting/#tickmode--array
• the multiplications are equivalent to your requirements, just generating arrays of appropriate length (ten ticks)

import numpy as np
import plotly.express as px

xg = np.random.rand(100, 1200)
fig = px.imshow(xg, aspect="auto",color_continuous_scale='ice')

# y1
fig.update_layout(yaxis={"tickmode":"array","tickvals":np.arange(10)*10, "ticktext":np.arange(10)*5}).show()
# y2
fig.update_layout(yaxis={"tickmode":"array","tickvals":np.arange(10)*10, "ticktext":np.arange(10)*50}).show()

supplementary - show both y-axis

• as per comment you can use documented approach https://plotly.com/python/multiple-axes/#multiple-axes
• you do require a trace per axis hence creation of two traces and modification of second trace to use y2
• setting second trace to "visible":False does not work. So there are two identical traces on top of each other

import numpy as np
import plotly.express as px

xg = np.random.rand(100, 1200)
fig = px.imshow(xg, aspect="auto", color_continuous_scale="ice").add_traces(
    px.imshow(xg, aspect="auto", color_continuous_scale="ice")
    .update_traces(yaxis="y2")
    .data
)

fig.update_layout(
    xaxis={"domain": [0.05, 1]},
    yaxis={
        "tickmode": "array",
        "tickvals": np.arange(10) * 10,
        "ticktext": np.arange(10) * 50,
    },
    yaxis2={
        "tickmode": "array",
        "tickvals": np.arange(10) * 10,
        "ticktext": np.arange(10) * 5,
        "anchor": "free",
        "position": 0,
        "autorange": "reversed",
    },
).show()