Adding a marker to a plot at specific points

Question

I have a dataframe(first few rows):

I can plot it with matplotlib.pyplot:

fig = plt.figure()
ax1 = fig.add_subplot(111,  ylabel='Price')

df1[['Close']].plot(ax=ax1)

To get:

What I would like to do is to add a marker to plot, down triangle, at the index 2018-09-10 04:00:00 which is indicated by the value -1 in the position column of the dataframe.

I tried to do this:

fig = plt.figure()
ax1 = fig.add_subplot(111,  ylabel='Price')

df1[['Close']].plot(ax=ax1)
ax1.plot(
    df1.loc[df1.positions == -1.0].index,
    df1.Close[df1.positions == -1.0],
    'v', markersize=5, color='k'
)

I get the plot like this:

So two things. One is that the index gets converted to something that shoots to year 2055, I don't understand why. Plus is there a way to add a marker at the specific position using just the first plot call? I tried to use markevery but with no success.

ImportanceOfBeingErnest · Accepted Answer · 2018-12-08 21:03:50Z

2

If you want to combine pandas plots and matplotlib datetime plots, the pandas plot needs to be plotted in compatibility mode

df1['Close'].plot(ax=ax1, x_compat=True)

That might give you the desired plot already.

If you don't want to use matplotlib, you can plot the filtered dataframe

df1['Close'].plot(ax=ax1)
df1['Close'][df1.positions == -1.0].plot(ax=ax1, marker="v", markersize=5, color='k')

answered Dec 8, 2018 at 21:03

ImportanceOfBeingErnest

342k61 gold badges737 silver badges771 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Kocur4d Over a year ago

Perfect. Thank you. Both suggestions are working. I will use the x_compat as it is just creating the markers. I didn't realise that pandas and matplotlib plots are different.

ImportanceOfBeingErnest Over a year ago

Well the plots are of course not different. But pandas may decide to use different units to plot dates.

Collectives™ on Stack Overflow

Adding a marker to a plot at specific points

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related