paste()与paste0()不仅可以连接多个字符串，还可以将对象自动转换为字符串再相连，另外还能处理向量
paste("fitbit", month, ".jpg", sep="")
#这个函数的特殊地方在于默认的分隔符是空格，所以必须指定sep=""，这样如果month=10时，就会生成fitbit10.jpg这样的字符串paste0函数，默认是sep=""(两个函数的唯一区别)
#要生成12个月的fitbit文件名
paste("fitbit", 1:12, ".jpg", sep = "")
[1] "fitbit1.jpg" "fitbit2.jpg" "fitbit3.jpg" "fitbit4.jpg" "fitbit5.jpg" "fitbit6.jpg" "fitbit7.jpg"
[8] "fitbit8.jpg" "fitbit9.jpg" "fitbit10.jpg" "fitbit11.jpg" "fitbit12.jpg"
#可以看出参数里面有向量时的捉对拼接的效果,如果某个向量较短,就自动补齐
a <- c("甲","乙","丙","丁","戊","己","庚","辛","壬","癸")
b <- c("子","丑","寅","卯","辰","巳","午","未","申","酉","戌","亥")
paste0(a, b)
[1] "甲子" "乙丑" "丙寅" "丁卯" "戊辰" "己巳" "庚午" "辛未" "壬申" "癸酉" "甲戌" "乙亥"paste与paste0还有一个collapse参数，可以把这些字符串拼成一个长字符串，而不是放在一个向量中
#collapse是合并成一个字符串时的分隔符
paste("fitbit", 1:3, ".jpg", sep = "", collapse = "; ")
[1] "fitbit1.jpg; fitbit2.jpg; fitbit3.jpg"