This page is a collection of small things I’ve learned over time. I find it useful to peruse to reinforce learning.

  • JSON uses double-quotes.
  • Type “iter " to insert a for loop in IntelliJ.
  • Java auto un boxing between primitive type and object type. For example: double to Double
  • EAV: entity attribute value (not just east Atlanta village)
  • used jvisualvm to connect to a running java app, make a heapdump, and then peruse it locally
  • check if rows 1 and 2 are exactly the same in excel:
    • =AND(EXACT(1:1, 2:2))
  • git log --grep
  • you can edit /etc/hosts to map 127.0.0.1 to something other than localhost
  • frequent itemsets (e.g. buying diapers & beer at the same time)
    • aka association rules
  • “spoonerism”: the transposition of initial or other sounds of words, as in a blushing crow for a crushing blow.
  • ICA (Independent Component Analysis):
    • does not assume that components will be orthogonal, but relies on assumption of statistical independence. accordingly, it’s good for BSS (Blind Source Separation) — aka identifying the sources of multiple microphones.
    • scikit-learn has FastICA
    • vs. PCA:
      • PCA wants each component to be gaussian, ICA wants each component to be as far from gaussian as possible
      • PCA ranks components by how much each accounts for variance (so it can be used for dimensionality reduction), but ICA does not
    • see: sci-kit learn and pg. 561 of Hastie, Tibshirani, Friedman
  • how could i use this to get the filenames as output?
    • ls -lat *venues*.csv | awk '{print $10}' | xargs head -n 1 {} | grep "state"
    • PS: use a for loop
  • when printing with css media queries, use position: absolute instead of fixed;
  • scikit-learn doesn’t have a 1-sided 2-sample kolmogorov-smirnov statistic. why?
  • Kleene Star: /* or ([0-9]*) (regex for “0” or “98765” or “”)
  • BNF: describe structure formally of, say, a postal e-mail address
  • strace: debug kernel-level activities (the zine from julia — jvns.ca)
  • use # in css to target media queries for accessing the screen element to determine display style