This is my day 5 homework for BIC by 生信星球.
Today's content is the introduction of data structure.
Before study, gain the demo data from wechat public account.
tips:
(1) the assignment symbol for R is <-, which can also be replaced by =. This answers my question in previous study.
(2) console equals command line in Linux
(3) the code in R includes (), which must be English input
(4) getwd() shows the working directory
(5) vector is made up of element which can be number or string
(6) table is called data frame (df) in R
(7) read help document by ?read.table, try example
(8) data type, focus on vector and data frame
1. vector
1.1 vector is a list of items that are of the same type
the associations among variable, item, vector.
代码语言：R复制x<- c(1,2,3)
x<- 1:10 # from 1 to 10 , 10 integers 1.2 extract items from vetor:
(1) by location
代码语言：R复制x[4] # the 4th item in x
x[-4] # reverse choose, exclude the 4th item in x and include others
x[2:4] #from 2nd to 4th
x[-(2:4)] # reverse choose
x[c(1,5)] # the 1st and 5th(2) by value
代码语言：R复制x[x==10] # item equals 10 in x
x[x<0] # items less than 0 in x
x[x %in% c(1,2,5)] # items in vector c(1,2,5)2. data frame
the demo data must be in the working directory
2.1 read local data
代码语言：R复制read.table(file = "huahua.txt", sep = "t", header = T)
a <- read.table(file = "huahua.txt", sep = "t", header = T)2.2 check line name, numbers of lines and colunms
代码语言：R复制colnames(a) #check the colunm name
rownames(a) # check the line name
dim(a) #check the structre of data frame2.3 save data frame
代码语言：R复制write.table(a, file = "yu.txt", sep = ",", quote = F)2.4 save vairables and load variables
代码语言：R复制save.image(file="bioinfoplanet.RData") #save current image
save(a,file="test.RData") # save a as test.RData
load("test.RData") # load test.RData2.5 extract items
by $ symbol
by location of coordinate
代码语言：R复制a[x,y] by name of colunm
代码语言：R复制a[x,]
a[,y]
a[c(a,b)] #a colunm and b colunm2,6 directly use the variables in data frame
代码语言：R复制plot(iris$Sepal.length, iris$Sepal.Width)save(a,file="test.RData") report: object a not found
check whether the object a is in the right-up section of Rstudio
