# set url path
students.file = "http://ifgi.uni-muenster.de/~epebe_01/Geostatistics/student_sample.csv"
# dowload locally
download.file(students.file, "students.csv", mode = "wb")
rm(students.file)
# read into R
students = read.csv("students.csv")
summary(students)
lapply(students,class)
# convert factor Weight to character:
students$Weight = as.character(students$Weight)
# replace "-" with appropriate NA ("not available", missing value flag in S)
students$Weight[students$Weight=="-"] = NA
# convert Weight to numeric
students$Weight = as.numeric(students$Weight)
# check classes:
lapply(students,class)
# remove missing records with missing values:
students = students[!is.na(students$Weight), ]
# first plot:
library(lattice)
xyplot(as.numeric(Weight)~as.numeric(Length)|Gender,students)
# compute bmi:
students$bmi = students$Weight / (students$Length/100)^2
histogram(~Weight | Gender,students)
histogram(~bmi | Gender,students)
summary(students)