plot1.R

# get data from csv file
household_power_consumption <- read.csv("C:/Users/wbuck/Desktop/R_stuff/exploratory analysis/data/household_power_consumption.txt", sep=";", stringsAsFactors = FALSE)

#subset data frame to only include two dates
hpc_to_use  <- household_power_consumption[household_power_consumption$Date %in% c("1/2/2007", "2/2/2007"), ]

#data comes in as strings, so convert all the fields that should be numeric to numeric 
hpc <- transform(hpc_to_use, Global_active_power = as.numeric(Global_active_power), 
                 Global_reactive_power = as.numeric(Global_reactive_power), Voltage = as.numeric(Voltage), 
                 Global_intensity = as.numeric(Global_intensity), Sub_metering_1 = as.numeric(Sub_metering_1),
                 Sub_metering_2 = as.numeric(Sub_metering_2), Sub_metering_3 = as.numeric(Sub_metering_3))

#convert the date field to actual date formats and create a combined datetime
hpc <- transform(hpc, Date = as.Date(Date, "%d/%m/%Y"))
hpc <- transform(hpc, datetime = as.character(paste(as.character(Date), Time)))
hpc <- transform(hpc, datetime = strptime(datetime, format = "%Y-%m-%d %H:%M:%S"))

#now for the plots
png(filename = "Plot1.png",
    width = 480, height = 480, units = "px", pointsize = 12,
    bg = "white")

hist(hpc$Global_active_power,col = "red", main = "Global Active Power", xlab = "Global active power (kilowatts)")

dev.off()