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# Éú³ÉÁ½¸öÊý¾Ý¿ò×öÑÝʾ
test1 <- data.frame(name = c('jimmy','nicker','Damon','Sophie'), 
                    blood_type = c("A","B","O","AB"))
test1

##     name blood_type
## 1  jimmy          A
## 2 nicker          B
## 3  Damon          O
## 4 Sophie         AB

test2 <- data.frame(name = c('Damon','jimmy','nicker','tony'),
                    group = c("group1","group1","group2","group2"),
                    vision = c(4.2,4.3,4.9,4.5))
test2

##     name  group vision
## 1  Damon group1    4.2
## 2  jimmy group1    4.3
## 3 nicker group2    4.9
## 4   tony group2    4.5

# ²Ù×÷֮ǰ¼ÇµÃÏȼÓÔØÕâ¸ö°üŶ
library(dplyr)

# ͨ¹ýÃû×ÖÈ¡Á½¸ö±í¸ñµÄ½»¼¯
inner_join(test1,test2,by = 'name')

##     name blood_type  group vision
## 1  jimmy          A group1    4.3
## 2 nicker          B group2    4.9
## 3  Damon          O group1    4.2

# ¶¼²¢ÔÚÒ»¿é»¹Éèɶ²ÎÊý£¬È¡²»µ½¾Í»á·µ»ØNA
full_join(test1,test2)

##     name blood_type  group vision
## 1  jimmy          A group1    4.3
## 2 nicker          B group2    4.9
## 3  Damon          O group1    4.2
## 4 Sophie         AB   <NA>     NA
## 5   tony       <NA> group2    4.5

left_join(test1,test2,by="name") # ±£Áô×ó±ß±í¸ñÀïµÄÄÇËĸöÈË£¬È¡²»µ½¾Í·µ»ØNA

##     name blood_type  group vision
## 1  jimmy          A group1    4.3
## 2 nicker          B group2    4.9
## 3  Damon          O group1    4.2
## 4 Sophie         AB   <NA>     NA

right_join(test1,test2,by="name") # ´ó¼Ò¿´ÏÂÇø±ð°É£¬¾ÍÊÇ»»ÏÂλÖÃ

##     name blood_type  group vision
## 1  jimmy          A group1    4.3
## 2 nicker          B group2    4.9
## 3  Damon          O group1    4.2
## 4   tony       <NA> group2    4.5