reindexing error when using method='ffill'

Question

ValueError: index must be monotonic increasing or decreasing [Jupyter Notebook Image][1]

I am practicing the above code snippet from the book python for data analysis by Wes McKinney

I create a DataFrame like this

frame=DataFrame(np.arange(9).reshape((3,3)), index=['a','c','d'], columns=['Ohio','Texas','California'])

when I try to reindex it like this:

states=['Texas','Utah','California']
frame.reindex(index=['a','b','c','d'],method='ffill', columns=states)

why is ValueError being raised?

Need more information. How does the original dataframe look like? — abhilb, Sep 23 '19 at 19:54
Possible duplicate of [ValueError: index must be monotonic increasing or decreasing](https://stackoverflow.com/questions/31285508/valueerror-index-must-be-monotonic-increasing-or-decreasing) — OverLordGoldDragon, Sep 23 '19 at 20:48
Because the `columns` index is not monotonic, as the error message says. — Stop harming Monica, Sep 24 '19 at 11:20

score 1 · Answer 1 · answered Mar 26 '21 at 14:53

1

You can use

frame.reindex(index=['a', 'b', 'c', 'd'], columns=states).ffill()

answered Mar 26 '21 at 14:53

Puyi

1 Answers1