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Hi i have the following data set. the data is large and here i am presenting the 1st 30 data. it is a time series of water level data with 15minute interval.

datetime time (min) time(Sec) WL (mm)
0 1/2/2021 0:00:00 0 7109.380
1 1/2/2021 0:15:00 900 7108.028
2 1/2/2021 0:30:00 1800 7107.959
3 1/2/2021 0:45:00 2700 7109.185
4 1/2/2021 1:00:00 3600 7109.045
5 1/2/2021 1:15:00 4500 7110.831
6 1/2/2021 1:30:00 5400 7110.585
7 1/2/2021 1:45:00 6300 7110.997
8 1/2/2021 2:00:00 7200 7109.854
9 1/2/2021 2:15:00 8100 7109.671
10 1/2/2021 2:30:00 9000 7110.530
11 1/2/2021 2:45:00 9900 7110.583
12 1/2/2021 3:00:00 10800 7111.532
13 1/2/2021 3:15:00 11700 7110.585
14 1/2/2021 3:30:00 12600 7111.124
15 1/2/2021 3:45:00 13500 7111.877
16 1/2/2021 4:00:00 14400 7110.813
17 1/2/2021 4:15:00 15300 7112.031
18 1/2/2021 4:30:00 16200 7113.617
19 1/2/2021 4:45:00 17100 7111.739
20 1/2/2021 5:00:00 18000 7112.435
21 1/2/2021 5:15:00 18900 7110.201
22 1/2/2021 5:30:00 19800 7111.451
23 1/2/2021 5:45:00 20700 7111.533
24 1/2/2021 6:00:00 21600 7112.126
25 1/2/2021 6:15:00 22500 7110.860
26 1/2/2021 6:30:00 23400 7112.207
27 1/2/2021 6:45:00 24300 7110.383
28 1/2/2021 7:00:00 25200 7110.979
29 1/2/2021 7:15:00 26100 7109.918

i want to make the frequency distribution with frequency unit in cycles per day, i have done it through another software as follows:

enter image description here

how can i make the frequency plot from the csv in python?

Engr M Faysal
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  • Hey! Could you label the axis of the graph corresponding to columns of the csv? – Ashok Arora May 31 '21 at 10:28
  • Hi, 5th column is the water level data. in every 15 min, the data is collected.. other three columns are the time in different formate.. so if i do the FFT.. the y axis will show the amplitude of water level and the x axis is the frequency which is cycles per day.. the water level is showing a signal with 2 cycles per day. that's why we can see a spike in 2cpd signal/.. Thanks – Engr M Faysal May 31 '21 at 11:29
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    cycles per day means one full wavelength in 24 hours. so 2 cpd means 2 full wavelengths in 24 hours or one full wavelength in 12 hours. In more general term, the period (T) is 24 (1 day) hours for 1 cpd and 12 hours for 2 cpd. – Engr M Faysal Jun 01 '21 at 11:21
  • How do you calculate the Cycles per day frequency? Do you use `np.fft.fft()`? Do you differentiate the input (the water levels measurements) prior to feeding it to the FFT function? – Paulo Schau Guerra Jun 01 '21 at 11:24
  • I have analysed the data with special software that uses the time steps and WL data to convert the time domain into the frequency domain. Thats why i am asking, how can i produce this plot using python.. – Engr M Faysal Jun 01 '21 at 15:36

0 Answers0