.apply(pd.to_numeric) returns error message
<p>I have a dataframe with two columns I want to convert to numeric type.  I use the following code:</p>

<pre><code>df[["GP","G"]]=df[["GP","G"]].apply(pd.to_numeric)
</code></pre>

<p>Python returns the following error message:</p>

<pre><code>File "C:\Users\Alexandros_7\Anaconda3\lib\site-packages\pandas\core\frame.py", line 4157, in _apply_standard
results[i] = func(v)

File "C:\Users\Alexandros_7\Anaconda3\lib\site-packages\pandas\tools\util.py", line 115, in to_numeric
coerce_numeric=coerce_numeric)

File "pandas\src\inference.pyx", line 612, in pandas.lib.maybe_convert_numeric (pandas\lib.c:53558)

File "pandas\src\inference.pyx", line 598, in      pandas.lib.maybe_convert_numeric (pandas\lib.c:53344)

ValueError: ('Unable to parse string', 'occurred at index GP')
</code></pre>

<p>How can I fix this problem?  How can I convert multiple column types at once with a command?  Thank you!</p>