iteration | 易学教程

The best way to iterate over sections of 2D arrays in Rust

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问题 I'm learning Rust by porting a small program that was written in C. It works with comparable performance to the C version. Still, I can't help but feeling my code could be better, hence this post. The following code solves a matrix equation using Gaussian elimination, which requires iterating over portions of an array. pub struct MatrixEquation { vec: Vec<f64>, mat: Vec<Vec<f64>>, } impl MatrixEquation { fn solve(&mut self) { let size = self.vec.len(); // Transform matrix to upper triangular

The best way to iterate over sections of 2D arrays in Rust

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r- How to use iteration on a custom function that uses dplyr

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问题 I want to create a custom function to calculate grouped percentages in a large dataset with 100+ columns. Because I have so many columns I want to do a loop or lapply or something to avoid typing the function out 100+ times. The function I wrote works fine when I type it in individually for each column, but I cannot figure out how to do it repeatedly. Here's a simplified dataframe and function: # load required libraries: library(tidyverse) df<-data.frame(sex=c('M','M','M','F','M','F','M',NA),

逻辑回归 - 欺诈检测

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import pandas as pd import matplotlib.pyplot as plt import numpy as np creditcard = 'C:/Users/Amber/Documents/唐宇迪-机器学习课程资料/机器学习算法配套案例实战/逻辑回归-信用卡欺诈检测/逻辑回归-信用卡欺诈检测/creditcard.csv' data = pd.read_csv(creditcard) print(data.head()) Time V1 V2 V3 ... V27 V28 Amount Class 0 0.0 -1.359807 -0.072781 2.536347 ... 0.133558 -0.021053 149.62 0 1 0.0 1.191857 0.266151 0.166480 ... -0.008983 0.014724 2.69 0 2 1.0 -1.358354 -1.340163 1.773209 ... -0.055353 -0.059752 378.66 0 3 1.0 -0.966272 -0.185226 1.792993 ... 0.062723 0.061458 123.50 0 4 2.0 -1.158233 0.877737 1.548718 ... 0.219422 0.215153 69.99 0 [5

Python: Prime numbers and the in range()

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问题 I am learning python and was looking at this problem: Python - Prime Number exercise Here are my questions: When n=2, the range will be (2,n), in the other words the range is between 2 and 2-1=1. for x in range(2, n): if n % x == 0: print("{} equals {} x {}".format(n, x, n // x)) return False else: print(n, "is a prime number") return True a. Will it be 2%2? b. If the number is even, it will print A equals B x C will the loop break once the condition is true or it will finish the loop? c. is

How to Iterate through Object inside Collection Meteor Mongo

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问题 If I do the following search: VideoCourses.find({'_id': 'jkwehrjewrew'}).fetch()[0].videos I get the following: Object {first: "firstvideo.html", second: "secondvideo.html", third: "thirdvideo.html"} My question, is how can iterate through the collection. I want to render one video at a time, so I can render the first video, and then on click, render the second, etc. The thing is, I have many sets of videos, so this should be done dynamically. It should iterate through the next video.first,

how to iterate $TwitterStatuses as an array or as Objects?

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问题 How can I iterate each $TwitterStatuses element/item/object? (And, how do I inspect each "status"?) Import-Module PSTwitterAPI Set-TwitterOAuthSettings -ApiKey $env:ApiKey -ApiSecret $env:ApiSecret -AccessToken $env:AccessToken -AccessTokenSecret $env:AccessTokenSecret #Get-TwitterUsers_Lookup -screen_name 'mkellerman' $TwitterStatuses = Get-TwitterStatuses_UserTimeline -screen_name 'mkellerman' #$TwitterStatuses = [array]Get-TwitterStatuses_UserTimeline -screen_name 'mkellerman' Foreach (

R or Python - loop the test data - Prediction validation next 24 hours (96 values each day)

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问题 I have a large dataset, below the training and test datasets train_data is from 2016-01-29 to 2017-12-31 head(train_data) date Date_time Temp Ptot JFK AEH ART CS CP 1 2016-01-29 2016-01-29 00:00:00 30.3 1443.888 52.87707 49.36879 28.96548 6.239999 49.61212 2 2016-01-29 2016-01-29 00:15:00 30.3 1410.522 49.50248 49.58356 26.37977 5.024000 49.19649 3 2016-01-29 2016-01-29 00:30:00 30.3 1403.191 50.79809 49.04253 26.15317 5.055999 47.48126 4 2016-01-29 2016-01-29 00:45:00 30.3 1384.337 48.88359

SQL iterating over a list to call EXEC on each item

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问题 Attempt to generalize my questions... I want to execute a stored procedure for each result returned by a SELECT statement. Mentally I want to try something like EXEC myStoredProc (SELECT id FROM sometable WHERE cond = @param) More details related to my specific case... I have a SaaS application. I would like to delete a tenant from the system. Before I can delete the tenant I must delete all records in the database associated with that tenant. Tenants own items such as Forms which contain

Why for var in array returns a string index? [duplicate]

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问题 This question already has answers here : javascript for loop counter coming out as string (3 answers) Closed 3 years ago . I've been really surprised that, in Javascript: > vals = ["a", "b", "c"] > for (v in vals) console.log(v + 1) 01 11 21 this because: > for (v in vals) console.log(typeof(v)) string string string so I'm forced to do something like: > for (v in vals) console.log(parseInt(v) + 1) 1 2 3 Why this happens? I know I can do > for (var v = 0; v < vals.length; v++) console.log(v +