Plot specific markers on plot in Python

Question

I have a plot that has on x axis time and on y axis values in percentages. The plot is drawn based on a dataframe output. As I would need to review many plots, would be good to insert some pointers of a different color. For example, each graph starts the timeline from 08:00 and finishes at 20:00. I would need a red marker at 12:00.

I have tried the following:

graph_df is a df that contains two columns: one with time and one with percentage data.

df = graph_df.loc[graph_df['time'] == "12:00"]
graph_df.plot(x="time", y="percentage", linewidth=1, kind='line')
plt.plot(df['time'], df['percentage'], 'o-', color='red')
plt.show()
plt.savefig(graph_name)

If I am using this section of the code, I am getting the marker at the correct percentage for 12:00, but always at the start of the timeline. In my case, the red dot is marked at 08:00, but with the right percentage associated.
Any idea why it's not correctly marked?

Thank you.

collinb9 · Accepted Answer · 2020-11-10 18:16:24Z

1

Converting the strings to datetime objects should work. Replacing your first line with

graph_df["time"] = pd.to_datetime(graph_df["time"]).dt.time
df = graph_df[graph_df["time"].apply(lambda time: time.strftime("%H:%M"))=='12:00']

should do the job

answered Nov 10, 2020 at 18:16

collinb9

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1 Comment

dante Over a year ago

It does exactly what I need. Thank you.

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