Q:

matplotlib histogram with frequency and counts

I have data (from a space delimited text file with two columns)  which is already binned but only a width of 1.  I want to increase this width to about 5.  How can I do this using numpy/matplotlib in Python?  
Using,
data = loadtxt('file.txt')
x = data[:, 0]
y = data[:, 1]
plt.bar(x,y)

creates too many bars and using,
plt.hist(data)

doesn't plot the histogram appropriately.  I guess I don't understand how matplotlib's histogram plotting works.
See some of the data below.
264 1
265 1
266 4
267 2
268 2
269 2
270 2
271 2
272 5
273 3
274 2
275 6
276 7
277 3
278 7
279 5
280 9
281 4
282 8
283 11
284 9
285 15
286 19
287 11
288 12
289 10
290 13
291 18
292 20
293 14
294 15

A:

What if you use numpy.reshape to transform your data before using plt.bar, for example:
In [83]: import numpy as np

In [84]: import matplotlib.pyplot as plt

In [85]: data = np.array([[1,2,3,4,5,6], [4,3,8,9,1,2]]).T

In [86]: data
Out[86]: 
array([[1, 4],
       [2, 3],
       [3, 8],
       [4, 9],
       [5, 1],
       [6, 2]])

In [87]: y = data[:,1].reshape(-1,2).sum(axis=1)

In [89]: y
Out[89]: array([ 7, 17,  3])

In [91]: x = data[:,0].reshape(-1,2).mean(axis=1)

In [92]: x
Out[92]: array([ 1.5,  3.5,  5.5])

In [96]: plt.bar(x, y)
Out[96]: <Container object of 3 artists>

In [97]: plt.show()

