When running my code I get the following message:
SettingWithCopyWarning:
A value is trying to be set on a copy of a slice from a DataFrame
See the the caveats in the documentation: http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy
df['detect'][df.index[0]] = df['event'][df.index[0]]
What is the correct way of setting the first value of a column equal to the first value of another column?
Use ix to perform the index label selection:
In [102]:
df = pd.DataFrame({'detect':np.random.randn(5), 'event':np.arange(5)})
df
Out[102]:
detect event
0 -0.815105 0
1 -0.656923 1
2 -1.417722 2
3 0.210070 3
4 0.211728 4
In [103]:
df.ix[0,'detect'] = df.ix[0,'event']
df
Out[103]:
detect event
0 0.000000 0
1 -0.656923 1
2 -1.417722 2
3 0.210070 3
4 0.211728 4
What you are doing is called chained indexing and may or may not work hence the warning
