Author: kostas

  • Learn some machine learning fundamentals in an afternoon

    Here is a plan to learn ML fundamentals in an afternoon by watching some videos on youtube: Follow this plan Machine learning fundamentals: What is Bias and Variance? – 6 minutes What is a Tensor? – 12 minutes [Stop and drink coffee, eat a snack] How to address bias and variance: Regularization (e.g. L2/Ridge) – […]

  • How to make interactive plots in Jupyter

    Python has great options for plotting data. However, sometimes you want to explore data by changing parameters and rerunning plots to explore the effect of those changed parameters. This slows down the cycle of exploration. Luckily, Jupyter offers you a way to make you plots interactive, so you can see the effect of parameter changes […]

  • Yummy 3D plots

    Very nice interactive 3D plots with Plotly. import plotly.graph_objects as go import numpy as np import pandas as pd # Read data from a csv Z = pd.read_csv('').values # Actually not necessary to provide X and Y… X = np.linspace(0, 1000, Z.shape[0]) Y = np.linspace(0, 1000, Z.shape[1]) fig = go.Figure(data=[go.Surface(x=X, y=Y, z=Z)]) fig.update_layout(title='Mt Bruno Elevation', […]

  • RM papers

    Optimal Dynamic Pricing of Inventories over Finite Horizons

  • How to create a versioned table from a crud table in Postgres with triggers

    Example You have a user table in Postgres: CREATE SCHEMA tutorial; CREATE TABLE tutorial.crud_users ( id INT NOT NULL, username VARCHAR NOT NULL, CONSTRAINT crud_table_pkey PRIMARY KEY (id) ); You insert new users and update usernames for existing users. Update is a destructive operation that overwrites data, so how do you keep track of what […]

  • Unusual instruments in Vietnam

    The nose flute The Duo A’Reng, a primitive talkbox!

  • Getting back into operations research

    For the last five years, I have been fascinated with machine learning techniques, but that fascination is slowly running out. I increasingly consider ML a tool in my tool box among others, not a panacea to all problems. In particular, I’d like to return to other algorithmic techniques from my educational back, i.e. computer science. […]

  • Good Book, Bad Program

    Programming is like writing a book. Both programs and books are written in a language, e.g. Datalog or Tagalog, but the similarity goes deeper than that. Imagine that you must write a book with the subject "a man walks his dog". There are endless ways to write that book, but only a few of them […]

  • Comparing the Corona outbreak in Scandinavia and South/South-East Asia

    I have read the WHO’s sitreps on CoViD-19 daily since the end of January 2020, where I was visiting Viet Nam. I now live in Denmark (a Scandinavian country) where the Corona virus has shut down society and many people have tested positive. When I compare the numbers for Scandinavia (Denmark, Norway, Sweden) with a […]

  • Our Sagawind 20

    Through hulls on Sagawind 20 This year we bought an old sail boat from 1979 – a Sagawind 20. My first order of concern is to check the location and state of the through hulls, which are perhaps the most critical part of a sail boat. There is literally a hole through the hull! Special […]