plot1.R

# assignment 1, plot 1

## make sure the folder exists
if (!file.exists("R_data")) { dir.create("R_data") }
## download the zip file
fileUrl <- "https://d396qusza40orc.cloudfront.net/exdata%2Fdata%2Fhousehold_power_consumption.zip"
download.file(fileUrl, destfile = ".\\R_data\\powerconsumption.zip", mode="wb")
## unzip the file
unzip(".\\R_data\\powerconsumption.zip", exdir = ".\\R_data")

## read the txt file into data frame, only the data needed
hps <- subset(read.table(".\\R_data\\household_power_consumption.txt", sep = ";", header = TRUE, stringsAsFactors = FALSE), Date == '1/2/2007' | Date == '2/2/2007')

# create a POXIS date
hps$DateTime<-strptime(paste(hps$Date, hps$Time), "%d/%m/%Y %T")

# data clean up, convert to numeric 
hpsclean <- transform(hps, Voltage = as.numeric(Voltage), Global_reactive_power=as.numeric(Global_reactive_power), Global_active_power = as.numeric(Global_active_power), Sub_metering_1 = as.numeric(Sub_metering_1), Sub_metering_2 = as.numeric(Sub_metering_2), Sub_metering_3 = as.numeric(Sub_metering_3))
                    
# plot 1
library(datasets)
png(file=".\\R_data\\plot1.png",width=480,height=480)
hist(hpsclean$Global_active_power, main="Global Active Power", xlab="Global Active Power(kilowatts)", col="RED")
dev.off()