条件语句

ifelse（条件，结果为yes执行的函数，结果为no执行的函数）

x = c(6:-4)
x
#ifelse（条件，结果为yes执行的函数，结果为no执行的函数）
ifelse(x>=0,x,NA)
sqrt(ifelse(x>=0,x,NA))

解释判断X>=0，如果结果为yes数值不变，如果结果为no数值变为NA

实例

ifelse可以多个嵌套

ifelse(ifelse(x>=0,x,NA)>3,x,NA)

嵌套实例

size <- c(0.05, 0.6, 0.3, 0.9)
# size <=0.2  Small
# 0.2< size <=0.8 Medium
# size >0.8 Large
ifelse(size<=0.2,"Small",ifelse(size<=0.8,"Medium","Large"))

嵌套实例2

应用实例

数据源

a=read.table("test.txt",header=T,sep="\t",row.names=1)
a
plot(a$height)
color=ifelse(a$gender=="male","blue","red")
color
plot(a$height,col=color)

代码执行结果
图

循环语句

for 和while

for (i in 1:5) print (1:i)

i=1
while(i<=5){
  print(1:i)
  i=i+1
}

实例

实际应用

#0.2小，0.2-0.8中，大于0.8为大
x <- c(0.05, 0.6, 0.3, 0.9)
for(i in 1:length(x)){
  if(x[i] <= 0.2){
    cat("Small\n")
  } else if(x[i] <= 0.8){
    cat("Medium\n")
  } else {
    cat("Large\n")
  }
}

genelist=c("TP53","EGFR","TGFB","MSH2","PTEN")
for(gene in genelist){
  filename=paste(gene,".pdf",sep="")
  cat(filename,"\n")
}

score=c(55,82,93,78,100,99,28)
for (i in 1:length(score)) {
  if(score[i]<60){
    cat("Poor\n")}
else if (score[i]<80){
  cat("Medium\n")}
else if (score[i]<90){
  cat("Good\n")}
else {
  cat("Excellent\n")}
  i=i=1
  }

score=c(55,82,93,78,100,99,28)
1:length(score)

for (i in 1:length(score)){
     if (score[i]<60) {
  cat("poor\n")}
  else if (score[i]<80) {
    cat("Medium\n")
  }
  else if (score[i]<90) {
    cat("Good\n")
  }
  else if (score[i]>=90) {
    cat("Excellent\n")
  }
}

ifelse 语句简化

ifelse(score>=90,"Excellent",ifelse(score>=80,"good",ifelse(score>=60,"Medium","poor")))