使用matplotlib的Python中的直方图

Question

I'm trying to make a histogram, and i've been doing some searches and trying to find the right code, but everything I try doesn't end up working. This is my code right now,

import matplotlib.pyplot as plt
import numpy as np

with open('gaubg.csv') as f:
       v = np.loadtxt(f, delimiter= ',', dtype="float", skiprows=1, usecols='None')

plt.hist(v, bins=100)
plt.xlabel("G-r0")
plt.ylabel('# of stars')
plt.title("Bottom half g-r0")

plt.show()

gaubg.csv is a csv file that includes about 600,000 (float, not int) data points that have to do with the color of stars. Every time I run this through python, this is the error message that shows up

Traceback (most recent call last): File "gaub.py", line 5, in v = np.loadtxt(f, delimiter= ',', dtype="float", skiprows=1, usecols='None') File "/sdss/ups/prd/numpy/v1_6_1/Linux/lib/python2.7/sitepackages/numpy/lib/npyio.py", line 794, in loadtxt vals = [vals[i] for i in usecols] TypeError: list indices must be integers, not str

I have no idea what that means. I've been trying to fix the code but I'm not sure how. If you could point out the obvious error(s) I'd be grateful!

Answer 1

usecols= 'None' 

should be

usecols= None

Or you can skip adding the usecols argument altogether. When you specified a string numpy tried to iterate through each character with the assumption that it's an integer.