Question

我想要一个for循环：

months = c("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December")
years = c(2018, 2019)

input = 17
for (i in 1:input) {
 output[i] = paste(months[i], years[i], sep = " ")????
 NEED HELP HERE. rep() ???

}

我希望输出为包含17个月的向量：

Output = c("January 2018", "February 2018", "March 2018", "April 2018", ... , "May 2019")

非常感谢您的帮助。

Answer 1

已经有系统提供的月份名称向量：month.name。由于粘贴是矢量化的并且可以回收，因此不需要for循环，并且粘贴的默认分隔符为“”，因此代码可以是：

 output <- paste( month.name, rep( years, each=12) )[1:17]
# test result ----
> output
 [1] "January 2018"   "February 2018"  "March 2018"     "April 2018"     "May 2018"       "June 2018"     
 [7] "July 2018"      "August 2018"    "September 2018" "October 2018"   "November 2018"  "December 2018" 
[13] "January 2019"   "February 2019"  "March 2019"     "April 2019"

另一种方法是将format应用于seq.Date结果：

 output <- format( seq( as.Date('2018-01-01'), as.Date('2019-04-01'), by="month") ,
                  "%B %Y" )   # argument to the format parameter for output
#---------------------

> output
 [1] "January 2018"   "February 2018"  "March 2018"     "April 2018"     "May 2018"       "June 2018"     
 [7] "July 2018"      "August 2018"    "September 2018" "October 2018"   "November 2018"  "December 2018" 
[13] "January 2019"   "February 2019"  "March 2019"     "April 2019"

请参见?seq.Date和?format.Date

Answer 2

另一个选择是：

> c(outer(month.name, 2018:2019, paste))[1:17]
 [1] "January 2018"   "February 2018"  "March 2018"    
 [4] "April 2018"     "May 2018"       "June 2018"     
 [7] "July 2018"      "August 2018"    "September 2018"
[10] "October 2018"   "November 2018"  "December 2018" 
[13] "January 2019"   "February 2019"  "March 2019"    
[16] "April 2019"     "May 2019"

Answer 3

c(paste(months,"2018"),paste(months,"2019"))[1:17]

 ## [1] "January 2018"   "February 2018"  "March 2018"     "April 2018"     "May 2018"       "June 2018"     
 ## [7] "July 2018"      "August 2018"    "September 2018" "October 2018"   "November 2018"  "December 2018" 
## [13] "January 2019"   "February 2019"  "March 2019"     "April 2019"     "May 2019"

对于循环帮助（R）

3 个答案: