Extract and plot data from a file in python

Question

I have some data stored in a file (xyz.dat) in the following format:

1   0.997790664988225E+000   0.100177762164687E+001   0.100034262755073E+001        
2   0.997788473973293E+000   0.100177969047903E+001   0.100034273413754E+001        
3   0.997782981718032E+000   0.100178486093194E+001   0.100034301665219E+001

What I want to do is, for each row, store the first column as x and rest of the values as y[1], y[2], y[3]...so on. Later I want to plot the data stored in y[n] for each row separately. I am new to python and have tried using split() but did not have much success. I am either not able to separate out the first column or at the end of each row there is a trailing '\n'. Any help will be really appreciated. Thanks in advance.

Martin Evans · Accepted Answer · 2018-03-16 07:55:53Z

1

You could read and plot as follows:

import matplotlib.pyplot as plt
import pandas as pd 

df = pd.read_csv('xyz.dat', sep=' ', header=None, usecols=(1, 2, 3)).T
df.plot(lw=0.5)
plt.show()

This would give you output:

Your 3 rows contain very similar data.

If the number of columns is unknown, you could just read it in normally and drop the first CSV column (actually first row after being transposed):

df = pd.read_csv('xyz.dat', sep=' ', header=None).T.drop(0)
df.plot(lw=0.5)
plt.show()

edited Mar 16, 2018 at 7:55

answered Mar 13, 2018 at 13:22

Martin Evans

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2 Comments

Aman_X Over a year ago

Thanks! What if the number of columns is unknown?

Martin Evans Over a year ago

In that case, don't use usecols, and drop the first CSV column using .drop(0)

quest · Accepted Answer · 2018-03-13 12:21:15Z

0

You can try:

import pandas as pd
import matplotlib.pyplot as plt
df = pd.read_fwf('file.dat')
plt.plot(df.iloc[:, 0], df.iloc[:,1])
plt.show()

You can go about plotting in the manner shown above. Hope this helps.

answered Mar 13, 2018 at 12:21

quest

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