Get arrays from Csv file to plot a chart

Question

I have this Csv file:

DateTime;S1;S2;S3
2020-07-15 16:27:01.221660;652.3826361765446;661.0531016851814;387.24703877989487
2020-07-15 16:27:01.221660;953.4271004457892;873.8955069132078;397.91143086810587

I want to read the file by columns, so:

DateTime_array = [2020-07-15 16:27:01.221660,2020-07-15 16:27:01.221660]
S1_array = [652.3826361765446,953.4271004457892]
S2_array = [661.0531016851814,873.8955069132078]
S3_array = [387.24703877989487,397.91143086810587]

After this I want to plot data, DateTime_array is the X coordinates for each Signal(S1,S2...) and in Signals array are contained the Y coordinates.

How can I do this? Is there any other way to do it straight from the csv?

You might need to have a look into pandas.read_csv

sushanth
– sushanth

2020-07-16 07:22:25 +00:00
Commented Jul 16, 2020 at 7:22 — sushanth
– sushanth, Commented Jul 16, 2020 at 7:22

Roim · Accepted Answer · 2020-07-16 07:50:33Z

1

Python's Pandas package is most convenient way to deal with data, including .csv files. You can easily read from you csv:

import pandas as pd
my_df = pd.read_csv(path, parse_dates=True)

(some adaptations may needed, as .csv has several formats. But this is right method to call)

Now you have a dataframe object looks exactly like your .csv file. It is easy to manipulate data. For example, if you just want to plot one column:

my_df.plot.scatter(x='DataTime', y='S1')

If you want a more complex plot you should use matplotlib package directly.

And if all you want is to save your data as an array:

DateTime_array = my_df["DataTime"].tolist()
S1_array = my_df["S1"].tolist()

As I said, when dealing with data - pandas' DataFrame object is the right way to manipulate data, so no need to extract values to arrays.

answered Jul 16, 2020 at 7:50

Roim

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2 Comments

Raj Srujan Jalem Over a year ago

The parse_dates flag of pandas read_csv does not parse datetime properly. A custom parser should be seperately provided to it.

Roim Over a year ago

My minor experience with parse_dates was absolutely fine. Thank you for this comment, I'm glad it's here if someone get stuck because of that flag

Raj Srujan Jalem · Accepted Answer · 2020-07-16 07:50:23Z

1

You can use Python's Pandas to solve your problem. This is what you need:

import pandas as pd

df = pd.read_csv(csv_file_path, sep=";")
df["DateTime"] = pd.to_datetime(df["DateTime"]) 
df.set_index("DateTime").plot()

answered Jul 16, 2020 at 7:50

Raj Srujan Jalem

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