Fix missing data value while joining dataframe in Python

Question

I am trying to join two dataframe one is data for choropleth with postcode and some other value in it another one is postcode and price.

I am trying to join both of them according to correspond postcode in map_df.

After I joined them, the prices are gone and all become NaN. How can I fix this?

Please see [how to make good reproducible pandas examples](https://stackoverflow.com/questions/20109391/how-to-make-good-reproducible-pandas-examples). Screenshots of data and/or code are discouraged here. — BigBen, Oct 19 '20 at 14:47
Mostly there are no prices for the records where `NaN` shows up, i.e. there are some postcodes available in `map_df` but not in `df`. Have you checked that? also you should use `merge` not `join` — Rafs, Oct 19 '20 at 15:08

score 0 · Answer 1 · answered Oct 19 '20 at 15:02

0

You should check merge documentation. I assume you want to do a inner join on post_code.

map_df.merge(df,how="inner",on=["post_code"])

answered Oct 19 '20 at 15:02

Maxime D.

This wouldn't do before renaming the merge column to `post_code` in both of `map_df` and `df` – Rafs Oct 19 '20 at 15:09

score 0 · Answer 2 · answered Oct 23 '20 at 07:19

0

I solved the problem by changing the type of data in my map_df dataframe. I changed the postcode column from "object" to "int64".

answered Oct 23 '20 at 07:19

Raymond Sim

2 Answers2