Error in plotting columns in dataframe

Question

I had a text file where I had few lines which I wanted to read in as pandas dataframe. Here are the few lines which I copied from the text file and saved into another text file

MTU, Time, Power, Cost, Voltage
MTU1,05/11/2015 19:59:06,4.102,0.62,122.4
MTU1,05/11/2015 19:59:05,4.089,0.62,122.3
MTU1,05/11/2015 19:59:04,4.089,0.62,122.3
MTU1,05/11/2015 19:59:06,4.089,0.62,122.3
MTU1,05/11/2015 19:59:04,4.097,0.62,122.4
MTU1,05/11/2015 19:59:03,4.097,0.62,122.4
MTU1,05/11/2015 19:59:02,4.111,0.62,122.5
MTU1,05/11/2015 19:59:03,4.111,0.62,122.5
MTU1,05/11/2015 19:59:02,4.104,0.62,122.5
MTU1,05/11/2015 19:59:01,4.090,0.62,122.4
MTU1,05/11/2015 19:59:00,4.093,0.62,122.4
MTU1,05/11/2015 19:58:59,4.112,0.62,122.5
MTU1,05/11/2015 19:58:58,4.107,0.62,122.6
MTU1,05/11/2015 19:58:57,4.092,0.62,122.7

Now, when I read in the text file using the following.

energy=pd.read_csv("energy.txt",sep=",")
# Reading in first 5 rows of data. 
energy.head()
Out[65]:

I get this:

MTU Time    Power   Cost    Voltage
0   MTU1    05/11/15 19:59  4.102   0.62    122.4
1   MTU1    05/11/15 19:59  4.089   0.62    122.3
2   MTU1    05/11/15 19:59  4.089   0.62    122.3
3   MTU1    05/11/15 19:59  4.089   0.62    122.3
4   MTU1    05/11/15 19:59  4.097   0.62    122.4

The problem is I guess the columns are still in the form of string. I converted them to numeric by using the following.

energy=energy.convert_objects(convert_numeric=True)

But when I try to plot power variable with time to see the trend by time,I get an error

energy.plot(energy.time,energy.power)

         if isinstance(obj, tuple) and is_setter:
   1142                         return {'key': obj}
-> 1143                     raise KeyError('%s not in index' % objarr[mask])
   1144 
   1145                 return _values_from_object(indexer)

KeyError: '[ 4.102  4.089  4.089  4.089  4.097  4.097  4.111  4.111  4.104  4.09\n  4.093  4.112  4.107  4.092  4.092  4.109  4.107  4.107  4.092  4.092\n  4.092  4.107  4.109  4.094  4.09   4.103  4.103  4.103  4.11   4.096\n  4.122  4.156  4.154  4.154  4.144  4.15   4.16   4.16   4.163  4.163\n  4.154  4.15   4.157  4.167  4.16   4.149  4.153  4.165  4.166  4.155\n  4.151  4.164  4.172  4.161  4.152  4.16   

I guess its because the power variable still has "\n" appended to some values. How do I rectify this error.

Answer 1

I'm on pandas 0.16 and it seems to be working fine for me. The column names do have a whitespace in the beginning of their names, though -

In [48]: energy
Out[48]: 
     MTU                 Time   Power   Cost   Voltage
0   MTU1  05/11/2015 19:59:06   4.102   0.62     122.4
1   MTU1  05/11/2015 19:59:05   4.089   0.62     122.3
2   MTU1  05/11/2015 19:59:04   4.089   0.62     122.3
3   MTU1  05/11/2015 19:59:06   4.089   0.62     122.3
4   MTU1  05/11/2015 19:59:04   4.097   0.62     122.4
5   MTU1  05/11/2015 19:59:03   4.097   0.62     122.4
6   MTU1  05/11/2015 19:59:02   4.111   0.62     122.5
7   MTU1  05/11/2015 19:59:03   4.111   0.62     122.5
8   MTU1  05/11/2015 19:59:02   4.104   0.62     122.5
9   MTU1  05/11/2015 19:59:01   4.090   0.62     122.4
10  MTU1  05/11/2015 19:59:00   4.093   0.62     122.4
11  MTU1  05/11/2015 19:58:59   4.112   0.62     122.5
12  MTU1  05/11/2015 19:58:58   4.107   0.62     122.6
13  MTU1  05/11/2015 19:58:57   4.092   0.62     122.7

In [49]: energy.columns
Out[49]: Index([u'MTU', u' Time', u' Power', u' Cost', u' Voltage'], dtype='object')

In [50]: energy.plot(x=' Time', y=' Power') # or energy.plot(' Time', ' Voltage')
Out[50]: <matplotlib.axes.AxesSubplot at 0x10847ffd0>

Here's the plot with x as Time and y as Power: