Index Error: too many indices for array While defining variable

Question

I received this message:

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-23-60bbe78150c2> in <module>()
      17 men_only_stats=data[0::4]!="male"
      18 
 ---> 19 women_onboard = data[women_only_stats,1].astype(np.float)
      20 men_onboard = data[men_only_stats,1].astype(np.float)
      21 proportion_women_survive= sum(women_onboard)/size(women_onboard)

 IndexError: too many indices for array

when I enter my code here:

import csv as csv
import numpy as np

csv_file_object = csv.reader(open(r"C:\Users\IT'S OVER 9000\Downloads\train.csv", 'rb'))
header = csv_file_object.next() 
data=[]

for row in csv_file_object:
    data.append(row)
data=np.array(data)

number_passengers= np.size(data[0::4,1].astype(np.float))
passengers_survived=np.sum(data[0::4,1].astype(np.float))
proportion_survived=passengers_survived/number_passengers

women_only_stats= data[0::4]=="female"
men_only_stats=data[0::4]!="male"

women_onboard = data[women_only_stats,1].astype(np.float)     
men_onboard = data[men_only_stats,1].astype(np.float)
proportion_women_survive= sum(women_onboard)/size(women_onboard)
proportion_men_survive= sum(men_onboard)/size(men_onboard)
print proportion_women_survive
print proportion_men_survive

Here are two lines of data from my cvs file:

PassengerId,Survived,Pclass,Name,Sex,Age,SibSp,Parch,Ticket,Fare,Cabin,Embarked,‌,,, 
1,0,3,"Braund, Mr. Owen Harris",male,22,1,0,A/5,21171,7.25,,S,,,     
2,1,1,"Cumings, Mrs. John Bradley (Florence Briggs Thayer)",female,38,1,0,PC,17599,71.2833,C85,C,,,

What did I do wrong, what caused it, and how do I fix it?

In the data set I have, there are only two categories: "male" and "female". If I put != "female" then python will grab the data with the gender index that is not female. But switching it to male accomplishes the same thing. — H0C
– H0C, Commented Sep 29, 2015 at 1:56
And it looks like both your variables contain female. != "male" is the same thing as == "female", isn't it? — Barmar
– Barmar, Commented Sep 29, 2015 at 1:58
oops. thanks for your help! Huh, just tried switching the variables and made men_only_stats= data[0::4] =="male" but i still get the indeces error. — H0C
– H0C, Commented Sep 29, 2015 at 1:59
what is the1 in women_only_stats,1 supposed to be? Get only the first column? — Anand S Kumar
– Anand S Kumar, Commented Sep 29, 2015 at 2:00

Anand S Kumar · Accepted Answer · 2015-09-29 03:03:31Z

0

Most probably, the issue in when you take the bool arrays (for indexing) -

women_only_stats= data[0::4]=="female"

I believe data is a 2D array, hence data[0::4] takes the every 4th row from the array (not the 4th column), and then you try to compare that with the string value, hence you get back an 2D array of True/False values. This causes the issue.

Actually what you want to do would be -

women_only_stats = data[:,4]=="female"

Same for men_only_stats , also you should reconsider everywhere where you have used [0::4] , this means every 4th element from that dimension.

Also , finally I would like suggest that for such kind of csv/data manipulation , it would be far easier to use pandas library than numpy.

edited Sep 29, 2015 at 3:03

answered Sep 29, 2015 at 2:24

Anand S Kumar

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Community · Accepted Answer · 2017-05-23 12:29:33Z

0

The error IndexError: too many indices for array happens when you try to access a 1d array as though it were 2d, or a 2d array as though it were 3d, etc.

In this case you are accessing data, a 1d array. The line throwing the error:

women_onboard = data[women_only_stats,1].astype(np.float)

...is using the syntax array_var[x,y], which can only be used for a 2d+ array. That syntax means you are accessing the element at row x and column y, so it doesn't apply to an array that has only one row (or only one column if you think of it that way).

If you search for that error message, you'll get lots of results of people asking similar questions, for example here, here, and here.

edited May 23, 2017 at 12:29

CommunityBot

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answered Sep 29, 2015 at 2:29

alksdjg

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