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Python Introduction to Data Visualization with Matplotlib Chart Toppers Scatter Plot

Jonathan Grieve
MOD
Jonathan Grieve
Treehouse Moderator 91,252 Points
Posted by Jonathan Grieve
Jonathan Grieve
Treehouse Moderator 91,252 Points

TypeError: The Scatter Chart is not being generated

I'm trying to generate the scatter chart as shown in the video but my cell keeps generating a TypeError in Jupyter. I can't what's gone wrong. Line 17 should allow me to use the list in this way shouldn't it?

from itertools import groupby

import csv
import matplotlib.pyplot as plt

input_file = 'iris.csv'

with open(input_file, 'r') as iris_data:
    irises = list(csv.reader(iris_data))

colors = {"Iris-setosa": "#2B5B84", "Iris-versicolor": "g", "Iris-virginica": "purple"}

irises.pop()

for species, group in groupby(irises, lambda i: i[4]):
    categorised_irises = list(group)
    sepal_lengths = [float(irises[0]) for iris in categorised_irises]
    sepal_widths = [float(irises[1]) for iris in categorised_irises]
    plt.scatter(sepal_lengths, sepal_widths, s=10, c=colors[species], label=species)

plt.title('Fisher\'s Iris Data Set', fontsize=12)
plt.xlabel('sepal length (cm)', fontsize=10)
plt.ylabel('sepal width (cm)', fontsize=10)
plt.legend(loc='upper right')

plt.show()

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-8-773bcecd5933> in <module>()
     15 for species, group in groupby(irises, lambda i: i[4]):
     16     categorised_irises = list(group)
---> 17     sepal_lengths = [float(irises[0]) for iris in categorised_irises]
     18     sepal_widths = [float(irises[1]) for iris in categorised_irises]
     19 plt.scatter(sepal_lengths, sepal_widths, s=10, c=colors[species], label=species)

<ipython-input-8-773bcecd5933> in <listcomp>(.0)
     15 for species, group in groupby(irises, lambda i: i[4]):
     16     categorised_irises = list(group)
---> 17     sepal_lengths = [float(irises[0]) for iris in categorised_irises]
     18     sepal_widths = [float(irises[1]) for iris in categorised_irises]
     19 plt.scatter(sepal_lengths, sepal_widths, s=10, c=colors[species], label=species)

TypeError: float() argument must be a string or a number, not 'list'

1 Answer

Jennifer Nordell
seal-mask
STAFF
.a{fill-rule:evenodd;}techdegree
Jennifer Nordell
Treehouse Teacher
Jennifer Nordell
.a{fill-rule:evenodd;}techdegree
Jennifer Nordell
Treehouse Teacher

Hi there, Jonathan Grieve! It seems like you have a typo. The variable irises is a list which contains other lists. The variable you're looking for is iris.

You wrote:

sepal_lengths = [float(irises[0]) for iris in categorised_irises]

But I believe that should be:

sepal_lengths = [float(iris[0]) for iris in categorised_irises]

Hope this helps! :sparkles:

Jonathan Grieve
Jonathan Grieve
Treehouse Moderator 91,252 Points
Jonathan Grieve
Jonathan Grieve
Treehouse Moderator 91,252 Points

Thanks for your help with this. It's truly amazing what I don't see sometimes when I'm coding! :)

Mark Chesney
Mark Chesney
11,747 Points

Hi Jennifer, if you have any clues as to my similar but different ValueError, they would be gladly appreciated!