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require(lubridate)
require(plyr)
require(ggplot2)
theme_set(theme_bw())

# create random dataset
df <- data.frame(DATETIME = ymd("2000-01-01") + ddays(runif(100)*365*5))

# compute day/month columns
df <- mutate(df,

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assign.events <- function(df, datetime.name="DATETIME", value.name="VALUE", interevent=8, threshold=0.1) {
  # assigns events to data frame such as storm events or discharge events
  require(plyr)
  if (!(datetime.name %in% names(df))) {
    stop(paste0('Could not find datetime column called ', datetime.name))
  }
  if (!(value.name %in% names(df))) {
    stop(paste0('Could not find value column called ', value.name))
  }
  if (!is.regular(df[, datetime.name])) {

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zoo.regular <- function(dates, values, by="hour", fill=NA) {
  # convert time series to regular zoo object
  require(zoo)
  z <- zoo(values, dates)
  z <- merge(z, zoo(, seq(floor_date(start(z), 'day'),
                          ceiling_date(end(z), 'day'),
                          by)), 
             fill=fill)
  z <- z[1:(length(z)-1)]
  return(z)

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is.regular <- function(x) {
  # returns TRUE if vector x of POSIXct datetimes is continuous and regular
  # by checking if there are more than one unique difftime between each row
  x.difftime <- difftime(x[2:length(x)], x[1:(length(x)-1)], units='secs')
  if (length(levels(factor(x.difftime))) > 1) {
    return (FALSE)
  } else {
    return (TRUE)
  }
}

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import pandas as pd
import csv

colspecs = [(0,11), (12,20), (21,30), (31,35), (36,40), (41,45)]
df = pd.read_fwf('ghcnd-inventory.txt', colspecs=colspecs, header=None, index_col=None)
df.columns = ["ID", "LATITUDE", "LONGITUDE", "ELEMENT", "FIRSTYEAR", "LASTYEAR"]
df.set_index("ID", inplace=True)
df.to_csv('ghcnd-inventory.csv', quoting=csv.QUOTE_NONNUMERIC)

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// log DHT sensor readings to SD card
#include "DHT.h"
#include <SD.h>
#include <Wire.h>
#include "RTClib.h"

RTC_DS1307 RTC;

// how many milliseconds between grabbing data and logging it. 1000 ms is once a second
#define LOG_INTERVAL  60000 // mills between entries (reduce to take more/faster data)

walkerjeffd

# Raspberry Pi Set Up Shell Script
# By Jeff Walker

# I created this to make it easier to re-install/re-configure my pi in case I need to start from scratch.
# Assumes Occidentalis v0.2 is being used.

# Run an update
# sudo apt-get update

# Adafruit WebIDE

walkerjeffd

R Programming for Environmental Engineers

Jeff Walker, PhD

This document provides some suggestions and resources for environmental engineers using R. This information is based on my own personal experience of learning and using R.

Software

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walkerjeffd

Configure Synology NAS as Git Server

Instructions for setting up a git server on a Synology NAS with Diskstation. Specifically, I am using a DS414 with DSM 5.0.

Set Up User and Folder

• Create user gituser via Diskstation interface (with File Station and WebDAV privilages)
• Add new shared folder called git (located at /volume1/git) with read/write access for gituser and admin. This folder will hold all the repos.
• Install Git Server package via Diskstation