Creating columns after converting list to an array

Question

My question is how do I convert the first four columns to floats and the last column to string? the kicker is that I cant use Pandas or CSV, I can only use numpy. How would I go about this? I have converted list into an array and currently displays:

'5.0,3.0,1.6,0.2,Iris-setosa'

I need to add the proper column headings as well, any input would be appreciated. Thanks!

import numpy as np

training_data = open("C:\Users\Angel\Downloads\iris-training-data.csv")
training_data_list = []

for elements in training_data:
    training_data_list.append(elements)


training_data_array = np.array(training_data_list)

print "The shape is {}\n".format(training_data_array.shape)

print "The visual array is: {}".format(training_data_array)

Is that one row of many? I'm assuming they are trying to get you to use a structured array so that you can have mixed dtypes — roganjosh
– roganjosh, Commented Sep 18, 2018 at 6:49

Jack Daniels · Accepted Answer · 2018-09-18 06:00:40Z

1

I think this is what you are looking for

import csv
with open('path_to_csv', newline='') as file:
data = csv.reader(file, delimiter=' ')
for row in data:
    row = row[0].split(',')
    r = [float(item) for item in row[:4]]
    r.append(str(row[4]))
    print(r)

This is my output, but I ran it for 9 columns rather than your 5. But it is same data set. The code I have put out will work for you.

[7.2, 0.805555556, 3.0, 0.416666667, 5.8, 0.813559322, 1.6, 0.625, 'virginica']
[7.4, 0.861111111, 2.8, 0.333333333, 6.1, 0.86440678, 1.9, 0.75, 'virginica']
[7.9, 0.9999, 3.8, 0.75, 6.4, 0.915254237, 2.0, 0.791666667, 'virginica']
[6.4, 0.583333333, 2.8, 0.333333333, 5.6, 0.779661017, 2.2, 0.875, 'virginica']
[6.3, 0.555555556, 2.8, 0.333333333, 5.1, 0.694915254, 1.5, 0.583333333, 'virginica']

answered Sep 18, 2018 at 6:00

Jack Daniels

1331 gold badge2 silver badges13 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Onecam Over a year ago

well this would work but I cant import CSV, the only import I can do is NUMPY

Jack Daniels Over a year ago

So you can only use numpy?

roganjosh Over a year ago

@Onecam you should mention these restrictions in your question. The csv module is part of the standard library, there's no reason for us to assume you can't use it.

Onecam Over a year ago

yeah @jack, nothing else. that is why its complicated

Onecam Over a year ago

@rogan, you are correct sir, my apologies, I have updated my post

|

Leo K · Accepted Answer · 2018-09-18 06:22:30Z

0

AFAIK, a fundamental part of numpy is that its arrays are homogeneous (each element has exactly the same type).

If you need an extra row (such as headings) or a column (as your last column that is a string) with a different type, you will have to keep them in separate numpy arrays.

You can convert the numeric part of your input from string to float using the astype method, e.g.:

string_col = traninig_data_array[:,4] # the last column
numbers = training_data_array[:,:4].astype(dtype=np.float64)

answered Sep 18, 2018 at 6:22

Leo K

5,3843 gold badges14 silver badges27 bronze badges

Collectives™ on Stack Overflow

Creating columns after converting list to an array

2 Answers 2

6 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

6 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related