lastsys
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Recent content on lastsysHugo -- gohugo.iosvWed, 14 Oct 2020 20:46:05 +0200Root
https://blog.lastsys.com/post/2020-10-14-root/
Wed, 14 Oct 2020 20:46:05 +0200https://blog.lastsys.com/post/2020-10-14-root/Root är ett brädspel som jag stiftade bekantskap med för över ett år sedan. Jag fastnade direkt. Spelets geniala asymetriska konstruktion gör att återspelbarheten är enorm. Varje spelare har nämligen sina helt egna spelregler.
Har man alla expansioner (The Riverfolk Expansion och The Underworld Expansion) leder det till åtta möjliga faktioner att välja bland. Reglerna har en hyfsad tröskel för att förstå till fullo och det är oftast bra att ha med sig någon som redan kan spelet.Bildskärm
https://blog.lastsys.com/post/2020-10-13-bildsk%C3%A4rm/
Tue, 13 Oct 2020 17:34:44 +0200https://blog.lastsys.com/post/2020-10-13-bildsk%C3%A4rm/Förra året valde jag att inreda en arbetsplats hemma. Det var ganska bra timing med tanke på hemarbetet som började i mars i år. Jag köpte då en 43" 4k skärm från Philips med VA-panel i tron att större är bättre. Nu efter ett år har jag valt att byta till en mindre skärm.
Problemet med 43" är att det är väldigt stort. Det är svårt att hålla koll på hela skärmen och de arbetsytor som ligger ute mot kanterna blir oanvända eftersom de hamnar i periferiseendet.Släktforskning
https://blog.lastsys.com/post/2020-10-12-slaktforskning/
Mon, 12 Oct 2020 18:02:02 +0200https://blog.lastsys.com/post/2020-10-12-slaktforskning/Jag har valt att gå över till att skriva på svenska. Det är enklare att skriva på sitt modersmål och jag bryr mig inte längre särskilt mycket om att nå ut till en internationell publik. Egentligen bryr jag mig inte särskilt mycket om huruvida någon läser detta alls.
Sedan något år tillbaka har jag släktforskat via MyHeritage. De har ett system som är enkelt att komma igång med, men jag saknar kontroll på vad som är korrekt och inte.Summer Books 2020
https://blog.lastsys.com/post/summer-books-2020/
Mon, 10 Aug 2020 08:00:00 +0200https://blog.lastsys.com/post/summer-books-2020/This summer I have spent much time reading both e-books and listening to audio books using Storytel. I have been able to read more books than ever making me very impressed of myself.
Title Author 1. Redovisningsavdelning Marviken Lars Wilderäng 2. Arbeta hemifrån i karantän: jobba effektivt Lars Wilderäng, Lena Wilderäng 3. Kampen om Romarriket Eva Queckfeld 4. Sveriges historia i korthet Peter Olausson 5. Englands historia 1-4 Dick Harrison 6.Om
https://blog.lastsys.com/about/
Sun, 26 Jul 2020 00:00:00 +0000https://blog.lastsys.com/about/Följ sidan med RSS. Varje sökväg har “index.xml” som gör att man kan prenumerera på godtyckliga delar av sidan.On the Vast Number of Finitely Possible Images - Part 2
https://blog.lastsys.com/post/on-the-vast-number-of-finitely-possible-images-part-2/
Mon, 28 Aug 2017 08:00:00 +0100https://blog.lastsys.com/post/on-the-vast-number-of-finitely-possible-images-part-2/I did some more digging into this subject trying to understand the complexity better. My reasoning starts with two color images and how many combinations there are depending on the number of white versus black pixels. It turns out that the distribution follows a binomial function no matter for any image dimensions. The following set of images shows the base 10 logarithms of the number of possible combinations as a function of the number of white pixels.On the Vast Number of Finitely Possible Images - Part 1
https://blog.lastsys.com/post/on-the-vast-number-of-finitely-possible-images-part-1/
Tue, 25 Jul 2017 10:13:00 +0100https://blog.lastsys.com/post/on-the-vast-number-of-finitely-possible-images-part-1/In my youth, around 25 years ago, I realized that a single digital image can be represented as a number. A 4-bit number has $$2^4 = 16$$ different combinations
and rearranging these patterns into 2x2 matrices yields
which can be interpreted as images where 0 is the first color index in a palette and 1 the second color index.
There is not an awful lot of information in these 16 tiles, but we can conclude the following principal patterns:Facebook has a bad Implementation of Groups
https://blog.lastsys.com/post/facebook-has-a-bad-implementation-of-groups/
Sat, 22 Jul 2017 08:05:00 +0100https://blog.lastsys.com/post/facebook-has-a-bad-implementation-of-groups/Introduction I used to have a Facebook account. I closed it many years ago since I thought it did not serve any meaningful purpose in my life. Recently I decided to get a new account since I needed access to several groups for various reasons. And after using Facebook Groups for several weeks, I must say I am very disappointed with their design decisions, although I understand why it is done this way.Excel Sheets Should be Immutable
https://blog.lastsys.com/post/excel-sheets-should-be-immutable/
Mon, 22 May 2017 09:00:00 +0100https://blog.lastsys.com/post/excel-sheets-should-be-immutable/If you have ever worked in an enterprise company you have probably witnessed usages of Microsoft Excel spreadsheets in ways you never would have imagined. I have. These spreadsheets could represent anything like budgets, resource planning, todo lists, project plans (Gantt), meeting protocols and requirements.
These ad-hoc solutions are signs of missing IT-systems in the organization. It is important to monitor the needs of users who invent their own solutions, especially when the number of users and/or the complexity of the spreadsheets becomes too large.Dynamic Vehicle Routing in Public Transportation
https://blog.lastsys.com/post/dynamic-vehicle-routing-in-public-transportation/
Sun, 21 May 2017 09:50:00 +0100https://blog.lastsys.com/post/dynamic-vehicle-routing-in-public-transportation/Planning public transportation is difficult. You have to decide where to locate stops and how to route vehicles to the stops to achieve good coverage while keeping capacity high, traveling time short and not breaking any laws of labor. Usually, the public transportation companies publish schedule updates a few times every year.
What if, given a set of stops, the timetables were planned dynamically based on actual demand? You (as a customer) would only need to order a trip between two stops and the system would tell you which vehicle to take and when to departure.Founding, Designing, and Running Cities
https://blog.lastsys.com/post/founding-designing-and-running-cities/
Sat, 20 May 2017 11:13:00 +0100https://blog.lastsys.com/post/founding-designing-and-running-cities/Think about it. When were cities founded? Will new cities be created? By whom were the modern cities built? How did our current cities grow and why did they grow the way they did (and still do)?
Cities started to appear during the Neolithic ages, some disappeared, and new ones were built. The location of a city is important since infrastructure and natural resources need to be available. The latest cities seem to have appeared during the industrialization period when peasants were looking for jobs in factories, leading to massive growth.Chromebooks vs. Android Tablets
https://blog.lastsys.com/post/chromebooks-vs-android-tablets/
Thu, 11 May 2017 08:00:00 +0100https://blog.lastsys.com/post/chromebooks-vs-android-tablets/I recently bought my first Chromebook. I was a bit worried that it might be too limited for me, but it is surprising how much time is spent in the browser. I can access special software using remote desktop connection to for example a stationary Windows 10 computer.
During my research of which Chromebook to get I settled on the ASUS Chromebook Flip C302 2-in-1 model with Intel-m3 CPU. The computer is passively cooled, and I really appreciate the noiseless experience.Types Representing Meaning Instead of Storage
https://blog.lastsys.com/post/types-representing-meaning-instead-of-storage/
Thu, 04 May 2017 08:50:00 +0100https://blog.lastsys.com/post/types-representing-meaning-instead-of-storage/Introduction I have a broad background in engineering not being raised in computer science. I am mostly autodidact in programming and software engineering which makes me sometimes think in other ways compared to genuine computer science people. During the past years, I have been jumping on the functional programming train and started learning the beauties of the constructions there in a similar way as I did with object oriented programming during the 1990s.Recap of the Last Four Years
https://blog.lastsys.com/post/recap-of-the-last-four-years/
Thu, 28 Jul 2016 12:00:00 +0100https://blog.lastsys.com/post/recap-of-the-last-four-years/Vacation. Four years later. I’ve meant to develop this blog with more content for some time, but a computer crash and life got in the way. I have been doing a lot of interesting things during this time. In 2013 I started modeling house prices in Sweden, first with Gaussian Processes but switched to regularized least squares using basis functions instead since 32GB of internal memory is not enough for GP in this application.Random Differential Equations
https://blog.lastsys.com/post/random-differential-equations/
Sat, 21 Jul 2012 12:00:00 +0100https://blog.lastsys.com/post/random-differential-equations/Last summer I read the book “Random Differential Equations in Science and Engineering” by T.T. Soong (1973). It handled a type of research which seems to have stagnated, and only so-called Stochastic Differential Equations (SDE) are researched. Apparently, Random Differential Equations (RDE) is a superset of SDEs and contain a set of interesting cases:
Differential equations with random initial conditions. Differential equations with stochastic input signals. Differential equations with random parameters.Gaussian Processes and Differential Equations
https://blog.lastsys.com/post/gaussian-processes-and-differential-equations/
Tue, 17 Jul 2012 12:00:00 +0100https://blog.lastsys.com/post/gaussian-processes-and-differential-equations/So, this is inevitable… Of course, I wanted to try to solve a differential equation using Gaussian Processes and at he same time finding the necessary control signal to pass through a given set of points. I am not 100% confident that I am doing all steps correct here, but it demonstrates how to proceed.
I am starting with a simple differential equation $$\frac{df(t)}{dt} = -a f(t) + u(t)$$ and given some measurements $$f(\tau)$$ for a set of times $$\tau$$ a solution for $$f(t)$$ and $$u(t)$$ is to be found.Estimating Derivatives for Gaussian Processes
https://blog.lastsys.com/post/estimating-derivatives-for-gaussian-processes/
Sun, 15 Jul 2012 12:00:00 +0100https://blog.lastsys.com/post/estimating-derivatives-for-gaussian-processes/In a previous post I wrote about basic Gaussian Processes. Sometimes it is of interest to also estimate the gradient and maybe have a confidence interval for that as well. For a given covariance function $$k(x_i,x_j)$$ and an estimated function $$f(x)$$ the following relations should hold:
$$\begin{array}{rcl} \text{cov} \left( f_i, \frac{\partial f_j}{\partial x_j} \right) & = & \frac{\partial k(x_i, x_j)}{\partial x_j} \ \text{cov} \left( \frac{\partial f_i}{\partial x_i}, f_j \right) & = & \frac{\partial k(x_i, x_j)}{\partial x_i} \ \text{cov} \left( \frac{\partial f_i}{\partial x_i}, \frac{\partial f_j}{\partial x_j} \right) & = & \frac{\partial^2 k(x_i, x_j)}{\partial x_i \partial x_j} \end{array}$$Gaussian Processes :: A Different Way to Explain Data
https://blog.lastsys.com/post/gaussian-processes-a-different-way-to-explain-data/
Sat, 14 Jul 2012 12:00:00 +0100https://blog.lastsys.com/post/gaussian-processes-a-different-way-to-explain-data/During my school years, we were taught to explain data points using least-squares regression. The basic formula for describing such a functional relationship is:
$$y = f(x) + \varepsilon$$
The simplest way to explain such a relationship is to assume an expression for $$f(x)$$ based on knowledge about the process. Assume that we have some measurements according to the plot below. Unless we have a sound knowledge about the way these measurements were acquired, we do not know if the points are describing a functional form exactly or if there should be a simple explanation with a lot of noise.