Plotly: Line and scatter in the same figure

Question

I have a pandas DataFrame with a DateTimeIndex and a numeric data column, from which I've created a line graph using px.line. I'd now like to highlight certain points on the line, and to do this I decided to overlay a scatter plot whose rows are a subset of the rows of the initial DataFrame.

I tried something like fig.add_trace(go.Scatter(x=df.index, y=df.col)) but this makes a new line on my line graph rather than a scatter plot. I also looked for a graph_objects function that makes a line graph but could not find it.

I've also observed that while I can make a scatter plot (that is, I see a bunch of points rather than a line) with px.scatter, even adding the above trace to an empty figure still creates a line graph. Maybe the solution here is as simple as passing the correct arguments to go.Scatter to get points instead of a line, but I'm not sure what that would be.

Answer 1

The default behavior of go.Scatter is to add markers and lines.

To plot only the points, you can instead pass the argument mode='markers' to go.Scatter:

fig.add_trace(go.Scatter(x=df.index, y=df.col, mode='markers'))

For example:

df = px.data.stocks()
fig = px.line(df, x='date', y="GOOG")
df_highlighted = df.iloc[50:60]
fig.add_trace(go.Scatter(x=df_highlighted['date'], y=df_highlighted['GOOG'], mode='markers'))