alexland

# at the R REPL prompt

devtools::install_github('IRkernel/repr')

devtools::install_github("IRkernel/IRdisplay")

devtools::install_github("IRkernel/IRKernel")

require(IRdisplay)

alexland

/**
 * Solves the n-Queen puzzle in O(n!)
 * Let p[r] be the column of the queen on the rth row (must be exactly 1 queen per row)
 * There also must be exactly 1 queen per column and hence p must be a permuation of (0 until i)
 * There must be n distinct (col + diag) and n distinct (col - diag) for each queen (else bishop attacks)
 * @return a Vector p of length n such that p[i] is the column of the queen on the ith row
 */
def nQueens(n: Int) = (0 until n).permutations filter {p =>   
  p.zipWithIndex.flatMap{case (c, d) => Seq(n + c + d, c - d)}.distinct.size == 2*n  
}

alexland

def xtab(*cols, apply_wt=False):
  '''
  returns:
    (i) xt, NumPy array storing the xtab results, number of dimensions is equal to 
        the len(args) passed in
    (ii) unique_vals_all_cols, a tuple of 1D NumPy array for each dimension 
        in xt (for a 2D xtab, the tuple comprises the row and column headers)
    pass in:
      (i) 1 or more 1D NumPy arrays of integers
      (ii) if wts is True, then the last array in cols is an array of weights

alexland

require(zoo)
require(xts)

#---------------------- mock an irregular (non-uniform interval) time series -----------------------#
start <- Sys.time() - (20 * 60 * 60)
end <- Sys.time()

# create the time series index
idx_ts = seq.POSIXt(start, end, by='hours')

alexland

/**
  * returns a transformed list (of strings) of the
  * 1-to-100 integer list passed in such that:
  *   integers evenly divisible by 3 are replaced by "fizz"
  *   integers evenly divisible by 5 are replaced by "buzz"
  *   integers evenly divisible by both 3 & 5 are replaced by "fizzbuz"
  *   all other integers are replaced by their string representation
  * */
def f[Int](q:List[Int]=(1 to 100).toList):List[String] = {
  fb.foldLeft(List[String]())( (u, v) =>

alexland

Magic words:

psql -U postgres

Most \d commands support additional param of __schema__.name__ and accept wildcards like *.*

• \q: Quit/Exit
• \c __database__: Connect to a database
• \d __table__: Show table definition including triggers

alexland

#!/bin/bash

#------------------------------------------------------------------------------
# Name:    sbtmkdirs
# Purpose: Create an SBT project directory structure with a few simple options.
# Author:  Alvin Alexander, http://alvinalexander.com
# Info:    http://alvinalexander.com/sbtmkdirs
# License: Creative Commons Attribution-ShareAlike 2.5 Generic
#          http://creativecommons.org/licenses/by-sa/2.5/
#------------------------------------------------------------------------------

alexland

# Bulk convert shapefiles to geojson using ogr2ogr
# For more information, see http://ben.balter.com/2013/06/26/how-to-convert-shapefiles-to-geojson-for-use-on-github/

# Note: Assumes you're in a folder with one or more zip files containing shape files
# and Outputs as geojson with the crs:84 SRS (for use on GitHub or elsewhere)

#geojson conversion
function shp2geojson() {
  ogr2ogr -f GeoJSON -t_srs crs:84 "$1.geojson" "$1.shp"
}

alexland

#---------------- custom install Apache Spark -------------------#

# instructions to build Apache Spark from source w/ current Scala & using sbt (vs maven)


# download Apache Spark src from the appropriate mirror


# untar:
tar zxf spark-1.3.1.tgz

alexland

package operator

object FunctionalPipeline {
  class PipedObject[T] private[Functional] (value:T)
    {
      def |>[R] (f : T => R) = f(this.value)
    }
    implicit def toPiped[T] (value:T) = new PipedObject[T](value)
}