ExData_Plotting1/plot4.R at master · Jacedeuce/ExData_Plotting1 · GitHub

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##Ensure that your working directory is set to an empty folder in your desired
##location before running plot1()
plot4 <- function(){

  #load required sqldf library.  sqldf is used to subset the desired
  ##days from large data file when loading the data
  library(sqldf)

  ##checks for data file and unzips it
  if(!file.exists("household_power_consumption.txt")){
    ##Data source
    dataURL <- "https://d396qusza40orc.cloudfront.net/exdata%2Fdata%2Fhousehold_power_consumption.zip"
    ##name downloaded file
    zipName <- "PowerConsumption.zip"
    ##download the file from the source
    download.file(dataURL, zipName, mode = "wb")

    ##Unzip the file into the set working directory
    unzip(zipName)
  }

  ##Assuming data is in a text file retrieves the name of the data file.
  ##if the data is stored in a different file type this code must be modified
  files <- list.files()
  file <- grep(pattern = "\\.txt", files, value = TRUE)

  ##Reads the data using an sql statement to select only the desired days from the data
  data1 <<- read.csv.sql(file, sql = "SELECT * FROM file
                        WHERE Date = '1/2/2007'
                        OR Date = '2/2/2007'", header = TRUE, sep = ";")
  closeAllConnections()

  ##Convert columns 3 to end to numeric
  numercol <- c(3:ncol(data1))
  data1[,numercol] <- as.numeric(as.character(unlist(data1[,numercol])))

  ##paste date and time fields into single column
  data1$datetime <- paste(data1$Date, data1$Time, sep=" ")

  ##use strptime() to convert datetime column into "POSIXlt" "POSIXt" format
  data1$POSdate <- strptime(data1$datetime, format = "%d/%m/%Y %H:%M:%S")

  ##sets graphic device to plot2.png output in repo folder - 480x480 pixels with transparent background
  png('./repo/plot4.png',width=480,height=480,units="px",bg = "transparent")

  ##creates 2 row and 2 column graphic device
  par(mfrow = c(2, 2))

    ##top left plot##
    plot(data1$POSdate,data1$Global_active_power, type = "n",  ylab = "Global Active Power", xlab = "")
      ##plots line of the Global Active Power vs Date
      lines(data1$POSdate,data1$Global_active_power)

    ##top right plot##
    plot(data1$POSdate,data1$Voltage, type = "n",  ylab = "Voltage", xlab = "datetime")
      ##plots line of Voltage vs Date
      lines(data1$POSdate,data1$Voltage)

    ##bottom left plot##
    plot(data1$POSdate, data1$Sub_metering_1, type = "n",  ylab = "Energy sub metering", xlab = "")
      ##plots lines of each sub-meter vs Date
      lines(data1$POSdate, data1$Sub_metering_1, col = "black")
      lines(data1$POSdate, data1$Sub_metering_2, col = "red")
      lines(data1$POSdate, data1$Sub_metering_3, col = "blue")
      ##adds legend on top right with lines and color coded
      legend(x="topright", lty = 1, legend = c(names(data1[,7:9])), col = c("black", "red", "blue"), bty="n")

    ##bottom right plot##
    plot(data1$POSdate,data1$Global_reactive_power, type = "n",  ylab = "Global_reactive_power", xlab = "datetime")
      ##plots line of Voltage vs Date
      lines(data1$POSdate,data1$Global_reactive_power)

  ##close connection to png
  dev.off()
}