Basic Assignment For R Programming

Basic Assignment For Programming and useful to coursera assignment1

dataset_url <- "http://s3.amazonaws.com/practice_assignment/diet_data.zip"
download.file(dataset_url, "diet_data.zip")
unzip("diet_data.zip", exdir = "diet_data")
list.files("diet_data")

##Andy

andy <- read.csv("diet_data/Andy.csv")
head(andy)
length(andy$Day)
dim(andy)
str(andy)
summary(andy)
names(andy)
andy[1, "Weight"]
andy[30, "Weight"]
andy[which(andy[,"Day"] == 30), "Weight"]
subset(andy$Weight, andy$Day == 30)
andy_start <- andy[1, "Weight"]
andy_end <- andy[30, "Weight"]
andy_loss <- andy_start - andy_end
andy_loss

##every body at once

files <- list.files("diet_data")
files

files_full <- list.files("diet_data", full.names = T)
files_full

head(read.csv(files_full[3]))

andy_david <- rbind(andy, read.csv(files_full[2]))
head(andy_david)
tail(andy_david)
day_25 <- andy_david[which(andy_david$Day == 25), ]
day_25

dat <- data.frame()
for (i in 1:5) {
dat <- rbind(dat, read.csv(files_full[i]))
}

str(dat)


for (i in 1:5) {
dat2 <- data.frame()
dat2 <- rbind(dat2, read.csv(files_full[i]))
}

str(dat2)
head(dat2)

median(dat$Weight, na.rm = T)
dat_30 <- dat[which(dat[, "Day"] == 30),]
dat_30
median(dat_30$Weight)

## The Real One

weightmedian <- function(directory, day) {
file_list <- list.files(directory, full.name = T)
dat <- data.frame()
for(i in 1:5) {
dat <- rbind(dat, read.csv(file_list[i]))
}
dat_subset <- dat[which(dat[, "Day"] == day), ]
median(dat_subset[, "Weight"], na.rm =T)
}

weightmedian(directory = "diet_data", day = 20)
weightmedian("diet_data", 4)
weightmedian("diet_data", 17)

summary(files_full)

##empty list
tmp <- vector(mode = "list", length = length(files_full))
tmp

for (i in seq_along(files_full)) {
tmp[[i]] <- read.csv(files_full[[i]])
}
str(tmp)

str(tmp[[1]])


##do.call() to combine tmp into a single data frame

output <- do.call(rbind, tmp)
str(output)