Creating a time-series plot with data in long format in python?

Question

I have time-series data in a pandas DataFrame that looks like this:

ID  HeartRate
1      120
1      118
1      115
2      98
2      110
2      112
3      128
3      115
3      90

And I want to create a separate line plot for each of the distinct IDs (i.e. patients). How can I go about this preferably using matplotlib? Will I have to create a "time-interval" variable?

df = my_data[['ID', 'HR']].copy() ## creating a new "mini" dataframe from the larger one that I've got. 

n_ids = df.ID.unique().size 
n_cols = int(n_ids ** 0.5) 
n_rows = int(n_ids + n_ids % n_cols) 
fig, axes = plt.subplots(n_rows, n_cols) 
for i, (ids, hr) in enumerate(df.groupby('ID')['HR']): 
hr.plot(ax=axes[i], title=f"ID:{idx}") 
fig.tight_layout()

However, as I get the following error:

'numpy.ndarray' object has no attribute 'get_figure'

yes, sorry forgot to mention that my data set has been imported as pandas dataframe — ummendial
– ummendial, Commented Mar 17, 2021 at 23:53
Does this answer your question? Plotting grouped data in same plot using Pandas — G. Anderson
– G. Anderson, Commented Mar 17, 2021 at 23:54
I don't think that it does because from what I can tell they are plotting the different distinct units on a single plot there and what I am looking to do is the contrary (unless I've missed something in the thread!) — ummendial
– ummendial, Commented Mar 18, 2021 at 0:00

fsl · Accepted Answer · 2021-03-18 15:24:35Z

3

Just groupby and plot it:

df.groupby('ID')['HeartRate'].plot()

Or using multiple axes, without worrying (so much at least) with the size of the category:

n_ids = df.ID.unique().size
n_cols = int(n_ids ** 0.5)
n_rows = n_cols + (1 if n_ids % n_cols else 0)                   
fig, axes = plt.subplots(n_rows, n_cols)
axes = axes.ravel()
for i, (idx, series) in enumerate(df.groupby('ID')['HeartRate']):
    series.plot(ax=axes[i], title=f"ID:{idx}")
fig.tight_layout()

Output:

edited Mar 18, 2021 at 15:24

answered Mar 17, 2021 at 23:55

fsl

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6 Comments

ummendial Over a year ago

But running this code, all the line graphs are in the sample plot. I am instead trying to create a distinct plot for each distinct ID.

fsl Over a year ago

No, I added a one-ID per-plot version.

ummendial Over a year ago

Yes, that's exactly what I was going for - sorry I might have missed that chunk of code the first time around. However, when I run the code I get the following error: AttributeError: 'numpy.ndarray' object has no attribute 'get_figure' - any idea on why this might be happening?

fsl Over a year ago

Can you post the exact code? You are likely mixing an array with an axe. Anyway why would want to get_figure if you already have it in the code I showed you?

fsl Over a year ago

It'll work if you do axes[0].get_figure() for example.

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