indexing

问题 Is there some way to make R use zero based indexing for vectors and other sequence data structures as is followed, for example in C and python. We have some code that does some numerical processing in C, we are thinking of porting it over into R to make use of its advanced statistical functions, but the lack(as per my understanding after googling) of zero based index makes the task a bit more difficult. 回答1: TL;DR: just don't do it! I don't think the zero/one-based indexing is a major

问题 Is there some way to make R use zero based indexing for vectors and other sequence data structures as is followed, for example in C and python. We have some code that does some numerical processing in C, we are thinking of porting it over into R to make use of its advanced statistical functions, but the lack(as per my understanding after googling) of zero based index makes the task a bit more difficult. 回答1: TL;DR: just don't do it! I don't think the zero/one-based indexing is a major

问题 I am currently going through the book "Hands-On machine learning... " by Aurèlion Gèron. However, I am getting the following error message: (it is somewhat cumbersome to reproduce because the following two CSV downloads are required: OECD IMF. Error message : File "C:\Users\xxx\Miniconda3\lib\site-packages\pandas\core\frame.py", line 4548, in set_index raise KeyError(f"None of {missing} are in the columns") KeyError: "None of ['Country'] are in the columns" The code: import matplotlib.pyplot

问题 Like many Postgres n00bs we have a lot of tables with foreign key constraints that are not indexed. I some cases this should not be a big performance hit - but this would be subject for further analysis. I have read the following article: https://www.cybertec-postgresql.com/en/index-your-foreign-key/ And used the following query to find all foreign keys without an index: SELECT c.conrelid::regclass AS "table", /* list of key column names in order */ string_agg(a.attname, ',' ORDER BY x.n) AS

问题 Let us consider the following data frame: import pandas as pd d = {'col1': [1, 2, 3], 'col2': [3, 4, 5]} df=pd.DataFrame(data=d) If I want to access the first element in pandas series df['col1'] , I can simply go df['col1'][0] . But how can I access the last element in this series? I have tried df['col1'][-1] which returns the following error: KeyError: -1L I know that I could go for something like df['col1'][len(df)-1] but why is reverse indexing impossible here? 回答1: For select last value

问题 Let us consider the following data frame: import pandas as pd d = {'col1': [1, 2, 3], 'col2': [3, 4, 5]} df=pd.DataFrame(data=d) If I want to access the first element in pandas series df['col1'] , I can simply go df['col1'][0] . But how can I access the last element in this series? I have tried df['col1'][-1] which returns the following error: KeyError: -1L I know that I could go for something like df['col1'][len(df)-1] but why is reverse indexing impossible here? 回答1: For select last value

问题 Let us consider the following data frame: import pandas as pd d = {'col1': [1, 2, 3], 'col2': [3, 4, 5]} df=pd.DataFrame(data=d) If I want to access the first element in pandas series df['col1'] , I can simply go df['col1'][0] . But how can I access the last element in this series? I have tried df['col1'][-1] which returns the following error: KeyError: -1L I know that I could go for something like df['col1'][len(df)-1] but why is reverse indexing impossible here? 回答1: For select last value

问题 I would like to develop a formula to construct a table of the top 5 titles / values within multiple groups, preferably without VBA. I have attached an example. Since I am new to this forum and require need at least 10 reputation points to post images, I have uploaded a screenshot to: http://i.imgur.com/v1LAkYk.png * Thanks @Scott Craner for adding the image to the post! I have already discovered and reviewed the following thread: Extracting top 5 maximum values (based on group) in excel.

问题 I would like to develop a formula to construct a table of the top 5 titles / values within multiple groups, preferably without VBA. I have attached an example. Since I am new to this forum and require need at least 10 reputation points to post images, I have uploaded a screenshot to: http://i.imgur.com/v1LAkYk.png * Thanks @Scott Craner for adding the image to the post! I have already discovered and reviewed the following thread: Extracting top 5 maximum values (based on group) in excel.

问题 After reading about query optimization techniques I came to know about the below techniques. 1. Indexing - bitmap and BTree 2. Partitioning 3. Bucketing I got the difference between partitioning and bucketing, and when to use them but I'm still confused how indexes actually work. Where is the metadata for index is stored? Is it the namenode which is storing it? I.e., actually while creating partitions or buckets we can see multiple directories in hdfs which explains the query performance