Plotting selected values from txt file in python

Question

I have a txt file which contains the datas corresponding to every second in every single day from year 2016-2018(everyday concluding about over 1400 datas), firstly, I selected the datas on a specifical day: 05.01.2016, then I want to draw a graph in python using the day's datas

the following code is for selecting values and drawing graph:

if '01.05.2016' in row: #select the value in day 05.01.2016
    x = [row.split()[6]] 
    y = [row.split()[2]]
fig = plt.figure()
ax1 = fig.add_subplot(111)
ax1.plot(x,y)
plt.ylim((200,800))
plt.show()

if I use the command:

x = [row.split()[6]] 
y = [row.split()[2]]
print(x,y)

then the x and y come will successfully come out(just some pairs x-y values as example):

['01.05.2016/15:43:00'] ['499']
['01.05.2016/15:44:00'] ['501']
['01.05.2016/15:45:00'] ['502']
['01.05.2016/15:46:00'] ['502']

a part of my original txt.file is like:

01.05.2016  15:43:00    499 U   42491,65486  -0,01   01.05.2016/15:44:00
01.05.2016  15:44:00    501 U   42491,65556  0,01   01.05.2016/15:45:00 
01.05.2016  15:45:00    502 U   42491,65625  0,02   01.05.2016/15:46:00 
01.05.2016  15:46:00    503 U   42491,65694  0,03   01.05.2016/15:47:00

But if I continue to write the command for drawing graph. the graph only show one pair(the last one pair) x-y value, my graph is like:

who can help me maybe?

@Bazingaa Thanks for your replying. Nope, the 4 lines are only example, actually there are about 1400 x-y values in 01.05.2616, I want it all as my x-y values. — It's Nele
– It's Nele, Commented Sep 24, 2018 at 12:44
Then show us what figure you are currently getting? It's hard to imagine what might be your problem — Sheldore
– Sheldore, Commented Sep 24, 2018 at 12:45
@It'sNele Use this: df['time'] = pd.to_datetime(df['time'], format='%d.%m.%Y/%H:%M:%S') — Joe
– Joe, Commented Sep 24, 2018 at 14:53
@Joe OMG, that works so good, thanks a lot!!! :))))))))))))))))))) — It's Nele
– It's Nele, Commented Sep 24, 2018 at 14:55

Community · Accepted Answer · 2020-06-20 09:12:55Z

You could do in this way:

import matplotlib.pyplot as plt
df = pd.read_csv('file.txt', sep = '\t', names = ["col", "col1", "val", "col3", "col4", "time"])
df['time'] = pd.to_datetime(df['time'], format='%d.%m.%Y/%H:%M:%S')
df.set_index('time', inplace=True)
match_timestamp = "01.05.2016"
df1 = df.loc[df.index.strftime("%m.%d.%Y") == match_timestamp]
print df1
df1['val'].plot()
plt.show()

Be careful which is your separator in pd.read_csv

Example

Input:

01.04.2016  15:46:00    503 42491,65694 0,03    02.05.2016/15:47:00
01.05.2016  15:43:00    499 42491,65486 -0,01   01.05.2016/15:44:00
01.05.2016  15:44:00    501 42491,65556 0,01    01.05.2016/15:45:00 
01.05.2016  15:45:00    502 42491,65625 0,02    01.05.2016/15:46:00 
01.05.2016  15:46:00    503 42491,65694 0,03    01.05.2016/15:47:00 
02.05.2016  15:46:00    503 42491,65694 0,03    02.05.2016/15:47:00

df1:

                            col      col1   val         col3   col4
time                                                               
2016-01-05 15:44:00  01.05.2016  15:43:00   499  42491,65486  -0,01
2016-01-05 15:45:00  01.05.2016  15:44:00   501  42491,65556   0,01
2016-01-05 15:46:00  01.05.2016  15:45:00   502  42491,65625   0,02
2016-01-05 15:47:00  01.05.2016  15:46:00   503  42491,65694   0,03

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