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Day: September 2, 2021

Using tsoutliers() to Detect Time Series Outliers

Rob J. Hyndman shows off a function in the forecast package in R:

The tsoutliers() function in the forecast package for R is useful for identifying anomalies in a time series. However, it is not properly documented anywhere. This post is intended to fill that gap.

The function began as an answer on CrossValidated and was later added to the forecast package because I thought it might be useful to other people. It has since been updated and made more reliable.

Read on to see how it works. This is one of the reasons I like the R programming language so much for data analysis and statistics: usually, somebody smarter than me has already built a solution to the problem and it’s just a matter of finding the right function. H/T R-Bloggers

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Solving the Knapsack Problem with PostgreSQL

Francesco Tisiot is packing for a trip:

People have had to pack luggage for a long time, so this optimization dilemma is far from new. It even has a name: the knapsack problem. It can be applied to a variety of use cases where there is a set of items with a defined weight (space occupied in the luggage in our example) and value (item benefits during holiday) and where the total weight is limited (luggage size).

The end goal is to come up with a set of items that fits within the weight constraint and has the maximum possible value.

Francesco provides us one possible solution to the problem. I like the knapsack problem a lot, but I like the Holyfield problem even more.

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Indexed Views and SARGability

Erik Darling shows how you can create indexed views to make life easier when tuning queries:

There are some things that, in the course of normal query writing, just can’t be SARGablized. For example, generating and filtering on a windowing function, a having clause, or any other runtime expression listed here.

There are some interesting ways to use indexed views to our advantage for some of those things. While windowing functions and having clauses can’t be directly in an indexed view, we can give an indexed view a good definition to support them.

It won’t always work, but it is an option to keep in mind.

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Accessing Network Shares from SQL Server

Daniel Hutmacher engages in chicanery:

Using a local service account for your SQL Server service, your server won’t automatically have permissions to access to other network resources like UNC paths. Most commonly, this is needed to be able to perform backups directly to a network share.

Using a domain account as your SQL Server service account will allow the server to access a network share on the same domain, but if the network share is not on your domain, like an Azure File Share, you need a different solution.

There’s a relatively easy way to make all of this work, though.

Click through to see how, as well as several methods to make it work within SQL Server.

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Adding Report Names to the Log Analytics Report

Gilbert Quevauvilliers feels complete:

I was really excited to use the Power BI Log Analytics for Analysis Services Engine report when it was released along with this blog post from the Power BI Team: Announcing long-term usage and performance insights (Public Preview) | Microsoft Power BI Blog | Microsoft Power BI

This is really a great report when using Log Analytics.

I found the one thing that I wanted to view was my report names. The standard report did not have this.

Protip: displaying GUIDs is not the same as displaying useful information. I recommend reading through this just to see how much pain and effort it takes to make the Log Analytics report actually become useful.

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