how to apply an index to a dataframe from another dataframe

Question

I can't seem to figure out how to build a dataframe from a series of new dataframes which all have the same index ( date ). I have the creation of the destination dataframe working properly BUT it's the changing of the index from 0...n to the dates that has me stumped.

I am building a dataframe df_new_sym

and adding it as a column to another dataframe

df_all_sym

this will continue for as many new columns are needed.

**df_new_sym** date iv_close_abs 0 2020-03-11 7.695 1 2020-03-12 22.172 2 2020-03-13 -8.108 3 2020-03-16 26.308

will CURRENTLY result in

**df_all_sym** type_a type_b 0 7.695 10.00 1 22.172 11.23 2 -8.108 14.78 3 26.308 9.98

I want the index of df_all_sym to be the date range coming from df_new_sym.

 date type_a type_b 2020-03-11 7.695 10.00 2020-03-12 22.172 11.23 2020-03-13 -8.108 14.78 2020-03-16 26.308 9.98

Please show your code, because I cannot guess what you did... — Serge Ballesta
– Serge Ballesta, Commented Apr 28, 2020 at 14:44
I had to remove the code as it was confusing people. I have the df_all_sym building correctly it's the INDEX problem that has me stumped — theakson
– theakson, Commented Apr 28, 2020 at 16:55

Mortz · Accepted Answer · 2020-04-28 15:39:41Z

3

just try the below code. It may solve the issue

df_all_sym = pd.merge(df_new_sym,df_all_sym,left_on='iv_close_abs',right_on='type_a',how='left')

followed by

df_all_sym = df_all_sym.set_index('date')

edited Apr 28, 2020 at 15:39

Mortz

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answered Apr 28, 2020 at 14:58

Nandan Rana

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2 Comments

theakson Over a year ago

Sorry I wasn't clear what the problem is. I can create the df_all_sym columns from the df_new_sym and that works fine. What is NOT happening is that the INDEX of df_all_sym should be the index of df_all_sym. I had tried setting the set_index approach but it doesn't work.

theakson Over a year ago

I changed the question to "hopefully" clarify the problem. It's the INDEX not the df_all_sym creation that's the issue.

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