ValueError: could not convert string to float: plotting a graph on python

Question

I've imported a csv file which all contain decimals with exponents for example (5.5006250364943992**02). I keep getting ValueError: could not convert string to float. This is what I have done:

import matplotlib.pyplot as plt
import csv
x = []
y = []
with open('DNSdata.csv', 'r') as csvfile:
    plots = csv.reader(csvfile, delimiter=',')
    for row in plots:
        x.append(float(row[0]))
        y.append(float(row[1]))
plt.plot(x, y, label='DNSdata')
plt.xlabel('x')
plt.ylabel('y')
plt.title('DNSdata')
plt.show()

show us what's in your csv file? A sample atleast?

void
– void

2017-06-27 11:59:49 +00:00
Commented Jun 27, 2017 at 11:59 — void
– void, Commented Jun 27, 2017 at 11:59

fjafjan · Accepted Answer · 2017-06-27 12:03:11Z

4

Is the Syntax you wrote the Syntax that is used in the file? I don't think Python can intepret "5.5**02".

If by "**" mean "10^" then you would need to manually make that replacement.

tmp = row[0].replace("**","e")
x.append(tmp)

answered Jun 27, 2017 at 12:03

fjafjan

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4 Comments

void Over a year ago

Nice noticing that..seems like that wouldve caused the problem+1!

gabriella Over a year ago

I tried what you said and it didn't work. so instead I changed all my values to values in this form '5.5006250364943992*10**(02)' and 5.5006250364943992*10^(02) instead of what i wrote in my question but still says that it can't convert string to float.

fjafjan Over a year ago

The problem is that Python does not intepret the string (5.5*10**3 is a valid expression in python, but not a valid formatting for a number string). Can you write the output or explain why my solution did not work? I tried it on my computer and it worked, but you would need to make the same replacement for the y values as well. The formatting you want is "E-notation" and if you don't want to change the CVS files you can easily change it in the code.

gabriella Over a year ago

It worked! thank you. You were right, it was the e notation that was the problem.

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