Get stated with R

1 LOi noi dau

Minh se huong dan cac buoc co ban

1. Tao moi truong (create working environment) and Doc du lieu vao R (read data)
2. Some basic skills

2 1. Tao moi truong (cho lan dau va no se duy tri mai voi 1 du an)

#Buoc 1
#Muc dich la no se luu cac lenh va mot so package)
#File>>>>New Project>>>New directory >>Emty project>>"ten project">>Va nguon chua thu vien cua minh.
#Luu y: tat ca ket qua hay file so lieu sau nay se luu o folder nguon nay

3 Doc du lieu vao R

#Buoc 2
#Thong thuong minh se doc file excel (xlsx hoac CSV) hoac cac file tu Stata (duoi la: .dta) hoac spss (.sav) hoac file text (.txt)...

#Neu minh da lam buoc 1 thi viec doc file se de dang hon

#a. Chay packages du minh doc bat cu file nao (thuong thi Dat nen luu file dang .csv hoac .dta)

#install.packages("foreign")  #chi install neu no chua co trong thu vien packages. 

#trong mot vai truong hop neu chua co packages thi nen tai no bang cach bam "Install" o goc phai duoi man hinh (click "install"the right down of your screen). Sau do go ten packages vao va bam install. Tiep theo la tat nhien phai suw dung cau lenh library("ten packages") nhu o duoi

library(foreign) #chay package moi install xong. Xong buoc nay thi minh co the doc bat cu file data dang nao

## Warning: package 'foreign' was built under R version 3.2.5

#b. Nhac cho R biet la minh dang lam viec tai nguon nao (tuc la folder nao)

getwd()  #no se bao minh dang sd folder nao

## [1] "C:/Users/BINH THANG/Dropbox/R - Learning"

#C. doc file du lieu vao va bat dau lam viec: Buoc quan trong nhat

data=read.csv("C:/Users/BINH THANG/Dropbox/R - Learning/pairdata.csv")  #data la ten moi minh dat cho file so lieu dang lam. No la ten moi bay gio

#ngoai ra neu doc loai file nao khac thi xem o day http://www.statmethods.net/input/importingdata.html 

4 Xem cac thong tin so lieu

#d. Muon xem cac thong tin file so lieu 

View(data) #cua so xuat hien va xem file so lieu

names(data) #xem cac bien so co

## [1] "Id"   "Post" "AHI"  "ODI"

## class of an object (numeric, matrix, data frame, etc): cac kieu so lieu co
class(data)

## [1] "data.frame"

## print first 10 rows of mydata (xem so lieu voi 10 quan sat dau tien)
head(data, n=10)

##    Id Post AHI ODI
## 1   1   T1  15 146
## 2   2   T1  15 149
## 3   3   T1  16 147
## 4   4   T1  16 146
## 5   5   T1  16 149
## 6   6   T1  16 148
## 7   7   T1  17 149
## 8   8   T1  16 148
## 9   9   T1  18 143
## 10  1   T2  22 216

##attach(data) # lenh nay thuong la bao la ta muon lay file nay

attach(data)

5 dinh nghia bien so

#doi voi cac bien dinh tinh thi minh can bao cho no hieu do la dih tinh; con neu la dinh luong thi thoi

data$Post=as.factor(data$Post) #bien Post la bien dinh tinh

6 tach bo so lieu voi cac bien so minhq uan tam (VD bo slieu minh co Id, Post, AHI, ODI). bay gio minh chi muon lay AHI va ODI)

dataMOI=subset(data, select=c(AHI, ODI))  #chi lay 2 bien AHI va ODI

attach(dataMOI)

## The following objects are masked from data:
## 
##     AHI, ODI

head(dataMOI)

##   AHI ODI
## 1  15 146
## 2  15 149
## 3  16 147
## 4  16 146
## 5  16 149
## 6  16 148

#con neu minh them dieu kien
dataMOI1=subset(data, select=c(AHI, ODI), Post="T1")  #chi lay 2 bien AHI va ODI va Post no phai la T1

attach(dataMOI1)

## The following objects are masked from dataMOI:
## 
##     AHI, ODI
## 
## The following objects are masked from data:
## 
##     AHI, ODI

head(dataMOI1)

##   AHI ODI
## 1  15 146
## 2  15 149
## 3  16 147
## 4  16 146
## 5  16 149
## 6  16 148

7 cac lenh ve mo ta tan so, % hay cac chi so khac thi Dat co them tham khao them o link nay: http://www.statmethods.net/stats/index.html

8 hoac vai cai cua minh co: http://rpubs.com/binhthang1001/260273

9 bai khac cua minh de o link nay http://rpubs.com/binhthang1001