Extracting column from Array in python

Question

I am beginner in Python and I am stuck with data which is array of 32763 number, separated by comma. Please find the data here data

I want to convert this into two column 1 from (0:16382) and 2nd column from (2:32763). in the end I want to plot column 1 as x axis and column 2 as Y axis. I tried the following code but I am not able to extract the columns

import numpy as np
import pandas as pd
import matplotlib as plt

data = np.genfromtxt('oscilloscope.txt',delimiter=',')
df = pd.DataFrame(data.flatten())
print(df)

and then I want to write the data in some file let us say data1 in the format as shown in attached pic

I can't write an answer right now but you could just split on your input string, then create the data frame with two columns using the array. You can use range (0:16382) on the array in order to define want is the content of each column. — Pomme De Terre
– Pomme De Terre, Commented Nov 14, 2020 at 10:59

piterbarg · Accepted Answer · 2020-11-14 12:05:21Z

1

It is hard to answer without seeing the format of your data, but you can try

data = np.genfromtxt('oscilloscope.txt',delimiter=',')
print(data.shape) # here we check we got something useful

# this should split data into x,y at position 16381
x = data[:16381]
y = data[16381:]


# now you can create a dataframe and print to file
df = pd.DataFrame({'x':x, 'y':y})
df.to_csv('data1.csv', index=False)

edited Nov 14, 2020 at 12:05

answered Nov 14, 2020 at 11:01

piterbarg

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5 Comments

piterbarg Over a year ago

so it should work except 32763 is an odd number and you need x,y to be of the same length. how do you want to deal with that?

Bholu Over a year ago

It was mistake from my side. I made it to read the x upto 16381 than this works. I wanted to write this into file again, so I wrote something like this (which is not writnf anything) time = str(x) ch1data = str(y) file = open("oscilloscope1.txt","w") file.write(time+ "\t" + ch1data) file.close

piterbarg Over a year ago

looks ok-ish except you probably want file.close() (note the parenthesis). This should write to a file but may not be in the format you want. how do you want it in the file? please provide a snippet of you desired output

Bholu Over a year ago

Thanks for the help, I have modified my question for the format

piterbarg Over a year ago

and I modified my answer

ML85 · Accepted Answer · 2020-11-14 11:03:47Z

0

Try this.

#input as dataframe df, its chunk_size, extract output as list. you can mention chunksize what you want.

def split_dataframe(df, chunk_size = 16382): 
    chunks = list()
    num_chunks = len(df) // chunk_size + 1
    for i in range(num_chunks):
    chunks.append(df[i*chunk_size:(i+1)*chunk_size])
return chunks

or

np.array_split

answered Nov 14, 2020 at 11:03

ML85

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