pandas reindex DataFrame with datetime objects
dataframe, pandas, python, reindex
Solution
It sounds like you don't want reindex. Somewhat confusingly `reindex` is not for defining a new index, exactly; rather, it looks for rows that have the specified indices. So if you have a DataFrame with index `[0, 1, 2]`, then doing a `reindex([2, 1, 0])` will return the rows in reverse order. Doing something like `reindex([8, 9, 10])` does not make a new index for the rows; rather, it will return a DataFrame with `NaN` values, since there are no rows with indices 8, 9, or 10.
It seems like what you want is to just keep the same rows, but make a totally new index for them. For that you can just assign to the index directly. So try doing `df.index = df['dtstamp']`.
Problem
Is it possible to reindex a pandas `DataFrame` using a column made up of datetime objects? I have a DataFrame `df` with the following columns: ``` Int64Index: 19610 entries, 0 to 19609 Data columns: cntr 19610 non-null values #int datflt 19610 non-null values #float dtstamp 19610 non-null values #datetime object DOYtimestamp 19610 non-null values #float dtypes: int64(1), float64(2), object(1) ``` I can reindex the `df` easily along `DOYtimestamp` with: `df.reindex(index=df.dtstamp)` and `DOYtimestamp` has the following values: ``` >>> df['DOYtimestamp'].values array([ 153.76252315, 153.76253472, 153.7625463 , ..., 153.98945602, 153.98946759, 153.98947917]) ``` but I'd like to reindex the DataFrame along `dtstamp` which is made up of datetime objects so that I generate different timestamps directly from the index. The `dtstamp` column has values which look like: ``` >>> df['dtstamp'].values array([2012-06-02 18:18:02, 2012-06-02 18:18:03, 2012-06-02 18:18:04, ..., 2012-06-02 23:44:49, 2012-06-02 23:44:50, 2012-06-02 23:44:51], dtype=object) ``` When I try and reindex `df` along `dtstamp` I get the following: ``` >>> df.reindex(index=df.dtstamp) TypeError: can't compare datetime.datetime to long ``` I'm just not sure what I need to do get the index to be of a datetime type. Any thoughts?