rapidsai/cudf

[FEA] Implement find_valid_index and its permutations (first_ and last_)

Open

#1,480 opened on Apr 22, 2019

View on GitHub
 (4 comments) (0 reactions) (0 assignees)C++ (735 forks)batch import
Pythonfeature requestgood first issue

Repository metrics

Stars
 (6,000 stars)
PR merge metrics
 (Avg merge 17d 21h) (230 merged PRs in 30d)

Description

Is your feature request related to a problem? Please describe. As a user, I'd like to be able to call last_valid_index or first_valid_index to get the index of the first/last non-null value in a Series.

Describe the solution you'd like I'd like to be able to do the following with cudf:

import pandas as pd
import numpy as np

ser1 = [1,2,3,4]
ser2 = [1,2,3,None]
pdf = pd.DataFrame({'a':ser1, 'b':ser2})
print(pdf.b.last_valid_index())
2

Additional context The pandas implementation is here. This will help with API compatibility.

Contributor guide

Research direction
Examine the pandas implementation of first valid index and last valid index in pandas/core/generic.py, then study how cuDF's Series class is structured to add similar methods.
Tech stack
python
Domain
backendapi
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Pythonpandas
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65