Loding CSV file and plotting histogram of a particular column

Aarthi,

For me to help further, you will need to provide a sample input file, and the script you are trying to use to read that input file. Then I can go from there.

-Sterling

···

On Feb 28, 2014, at 1:38PM, Aarthi Reddy wrote:

It is not an uppercase problem. The other two titles had combination of upper and lower case. All columns have the exact same number of lines and there are no empty entries.

On Feb 28, 2014, at 3:31 PM, Sterling Smith <smithsp@...3304...> wrote:

You have an uppercase 'Confidence'. Are you using pandas or numpy? For numpy, from Piet's email, you need a lowercase key. What does
`print df['Confidence'].shape`
yield? Because the error looks like you have an array with no size (zero dimensions), so perhaps you are still not reading in your file correctly.

-Sterling

On Feb 28, 2014, at 1:02PM, AR12 wrote:

Thanks, this worked for two of the columns. For the third column, I get this error: Sorry to bug you about this. Do you know where I can find the solution to this problem?

---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-10-ae5186552dfe> in <module>()
----> 1 plt.hist(df['Confidence'],bins=10)

/Library/Python/2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.9-intel.egg/matplotlib/pyplot.pyc in hist(x, bins, range, normed, weights, cumulative, bottom, histtype, align, orientation, rwidth, log, color, label, stacked, hold, **kwargs)
  2875 histtype=histtype, align=align, orientation=orientation,
  2876 rwidth=rwidth, log=log, color=color, label=label,
-> 2877 stacked=stacked, **kwargs)
  2878 draw_if_interactive()
  2879 finally:

/Library/Python/2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.9-intel.egg/matplotlib/axes/_axes.pyc in hist(self, x, bins, range, normed, weights, cumulative, bottom, histtype, align, orientation, rwidth, log, color, label, stacked, **kwargs)
  5477 xmax = -np.inf
  5478 for xi in x:
-> 5479 if len(xi) > 0:
  5480 xmin = min(xmin, xi.min())
  5481 xmax = max(xmax, xi.max())

TypeError: len() of unsized object

On Fri, Feb 28, 2014 at 2:42 PM, Paul Hobson-2 [via matplotlib] <[hidden email]> wrote:
Sounds like you want to use pandas, not numpy.

import pandas
import matplotlib.pyplot as plt
df = pandas.read_csv('myfile.txt', sep='\t')
plt.hist(data['A'], bins=30)

...should do it for you.

On Fri, Feb 28, 2014 at 11:06 AM, AR12 <[hidden email]> wrote:
Hi,

I have a csv file where head -5 looks like this:

A B C
100 0.45 0.3
67 0.25 0.4
50.6 0.2 0.6
56.4 0.4 0.3

The columns are tab separated. I want to load this CSV file and plot the
histogram of the third or second column. I was able to load the csv file
using this:
data=csv2rec('Downloads/Sample.txt',delimiter='\t',skiprows=0)
The file has 2792 rows including the top header row.

When I do

data['A'] I get this error:

---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-19-856828b8eaa3> in <module>()
----> 1 data['A']

/Library/Python/2.7/site-packages/numpy-1.9.0.dev_297f54b-py2.7-macosx-10.9-intel.egg/numpy/core/records.pyc
in __getitem__(self, indx)
   457
   458 def __getitem__(self, indx):
--> 459 obj = ndarray.__getitem__(self, indx)
   460 if (isinstance(obj, ndarray) and obj.dtype.isbuiltin):
   461 return obj.view(ndarray)

ValueError: field named A not found

First is data['A'] supposed to read the whole A column? Once I read the
column I want to be able to plot it. Can I simply do

hist(data['A'],bins=30) or something like that.

Many thanks,
AR

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