Chapter 2 - Filtering data¶
In the previous chapter, you learned how to read and print data that is a bit raw. Now, try to select a few columns and handle them properly.
Start with these two columns: Time (time) and Magnitude (mag). After getting the information from these columns, filter and adapt the data. Try formatting the date to Qt types.
There is not much to do for the Magnitude column, as it’s just a floating point number. You could take special care to check if the data is correct. This could be done by filtering the data that follows the condition, “magnitude > 0”, to avoid faulty data or unexpected behavior.
The Date column provides data in UTC format (for example, 2018-12-11T21:14:44.682Z), so you could easily map it to a QDateTime object defining the structure of the string. Additionally, you can adapt the time based on the timezone you are in, using QTimeZone.
The following script filters and formats the CSV data as described earlier:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39
import argparse import pandas as pd from PySide2.QtCore import QDateTime, QTimeZone def transform_date(utc, timezone=None): utc_fmt = "yyyy-MM-ddTHH:mm:ss.zzzZ" new_date = QDateTime().fromString(utc, utc_fmt) if timezone: new_date.setTimeZone(timezone) return new_date def read_data(fname): # Read the CSV content df = pd.read_csv(fname) # Remove wrong magnitudes df = df.drop(df[df.mag < 0].index) magnitudes = df["mag"] # My local timezone timezone = QTimeZone(b"Europe/Berlin") # Get timestamp transformed to our timezone times = df["time"].apply(lambda x: transform_date(x, timezone)) return times, magnitudes if __name__ == "__main__": options = argparse.ArgumentParser() options.add_argument("-f", "--file", type=str, required=True) args = options.parse_args() data = read_data(args.file) print(data)
Now that you have a tuple of QDateTime and float data, try improving the output further. That’s what you’ll learn in the following chapters.
© 2020 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners. The documentation provided herein is licensed under the terms of the GNU Free Documentation License version 1.3 as published by the Free Software Foundation. Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners.