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What Every Computer Scientist Should Know About Floating-Point Arithmetic makes the following claim:

Due to roundoff errors, the associative laws of algebra do not necessarily hold for floating-point numbers. For example, the expression (x+y)+z has a totally different answer than x+(y+z) when x = 10³⁰, y = -10³⁰ and z = 1 (it is 1 in the former case, 0 in the latter).

How does one reach the conclusion in their example? That is, that (x+y)+z=1 and x+(y+z)=0?

I am aware of the associative laws of algebra, but I do not see the issue in this case. To my mind, both x and y will overflow and therefore both have an integer value that is incorrect but nonetheless in range. As x and y will then be integers, they should add as if associativity applies.

I've finished my first semester in a college-level SQL course where we used "SQL queries for Mere Mortals" 3rd edition.

Long term I want to work in data governance or as a data scientist, so digging deeper is needed and I found the Stanford SQL course. Today taking the first mini quiz, I got the answers right but on these two I'm not understanding WHY I got the answers right.

My 'SQL for Mere Mortals' book doesn't even cover hash or tree-based indexes so I've been searching online for them.

I mostly guessed based on what she said but it feels more like luck than "I solidly understand why". So I've ordered "Introduction to Algorithms" 3rd edition by Thomas Cormen and it arrived last week but it will take me a while to read through all 1,229 pages.

Found that book in this other stackoverflow link =>https://stackoverflow.com/questions/66515417/why-is-hash-function-fast

Stanford Course => https://www.edx.org/course/databases-5-sql

I thought a hash index on College.enrollment would not speed up because they limit it to less than a number vs an actual number ?? I'm guessing per this link Better to use "less than equal" or "in" in sql query that the query would be faster if we used "<=" rather than "<" ?

This one was just a process of elimination as it mentions the first item after the WHERE clause, but then was confusing as it mentions the last part of Apply.cName = College.cName.

My questions:

1. I'm guessing that similar to algebra having numerators and denominators, quotients, and many other terms that specifically describe part of an equation using technical terms. How would you use technical terms to describe why these answers are correct.

2. On the second question, why is the first part of the second line referenced and the last part of the same line referenced as the answers. Why didn't they pick the first part of each of the last part of each?

For context, most of my SQL queries are written for PostgreSQL now within PyCharm on python but I do a lot of practice using the PgAgmin4 or MySqlWorkbench desktop platforms.

I welcome any recommendations you have on paper books or pdf's that have step-by-step tutorials as many, many websites have holes or reference technical details that are confusing.

Thanks

I tried to copy the preview animation Of StackOverflow which changes the jobs infinitely. My problem is when I clear Interval and then I start interval again I get some sort of delay, there's way to start the interval immediately after I cleared the previous ???

My backend returns the following data. For some data there is a hyperlink that i need to fetch in order to get the data. While that is for an single object quite straight forward. I struggle how i get the data out an array of objects.

I am trying to create a node-link diagram (decision tree) by using parsnip and tidymodels. What I am performing is building a decision tree model for the StackOverflow dataset using the tidymodels package and rpart as model engine. The model should predict whether a developer will work remotely (variable remote) based on the number of years of programming experience (years_coded_job), degree of career satisfaction (career_satisfaction), job title "Data Scientist" yes/no (data_scientist), and size of the employing company (company_size_number).

My pipeline

I have a set of pairs of record IDs and for each pair a corresponding probability that these records actually belong to each other. Each pair is unique, but any given ID may be part of more than one pairing.

E.g.:

We are developing a library where we want to allow users to easily develop their own objects that can interact with the rest of the library.

To give a concrete example, the APIs we created so far use a similar implementation as the one used in scikit-learn for building custom estimators (see https://scikit-learn.org/stable/developers/develop.html#apis-of-scikit-learn-objects and https://github.com/scikit-learn/scikit-learn/blob/15a949460/sklearn/base.py#L141). There, users can create their own estimators by subclassing from BaseEstimator and implementing their own fit method.

Similarly, in our library we have a basic abstraction that constitutes the "building block" of the library. We have implemented our own BaseClass as an abstract class, with several methods foo1, foo2 etc. already implemented, and an abstract method bar to be implemented by users:

I am trying to apply for jobs on jobserve using web scraping. After clicking apply on the web page, Selenium cannot locate any of the elements of the pop up:

I am trying to get the second last value in each row of a data frame, meaning the first job a person has had. (Job1_latest is the most recent job and people had a different number of jobs in the past and I want to get the first one). I managed to get the last value per row with the code below:

first_job <- function(x) tail(x[!is.na(x)], 1)

first_job <- apply(data, 1, first_job)