"Setting with copy warning"

Asked May 13 '15 at 21:34

Active May 13 '15 at 21:39

Viewed 113 times

I'm recently new to python. I've been trying to transform the date contents of a column into a new column containing the month and year which can the be grouped by a seaborn box plot function. Assume lcd_raw_clean is a pandas dataframe containing feature 'issue_d' which is datetime dtype.

The code I'm using

lcd_raw_clean['issue_YYMM'] = lcd_raw_clean['issue_d'].apply(lambda x: x.strftime('%Y%m'))

Generates the warning:

/Applications/anaconda/lib/python2.7/site-packages/IPython/kernel/__main__.py:7: SettingWithCopyWarning: 
A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead

I cannot understand why this generates this warning and how to get around it.

edited May 13 '15 at 21:39

Blckknght

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asked May 13 '15 at 21:34

GPB

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Well I can only think that `lcd_raw_clean` is a view or slice of your original df, can you post how `lcd_raw_clean` was created – EdChum May 13 '15 at 21:40
> lcd_raw_clean = lcd_raw[:-4] – GPB May 14 '15 at 02:32
I sliced the last 4 rows off as the data represented a footer. – GPB May 14 '15 at 02:33
Could you try `lcd_raw.iloc[:-4] = lcd_raw[:-4]['issue_d'].apply(lambda x: x.strftime('%Y%m')) ` – EdChum May 14 '15 at 08:40

"Setting with copy warning"

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