How recognize weekday depending on entry date-CodePudding

I have a simple question, but I wanted to know how to do it: I have a database and two input data (dmda and DTest):

df1 <- structure(
  list(date = c("2021-06-23","2021-06-24","2021-06-30","2021-07-01"),
       DTT= c("Hol","Hol","Hol",0),
       Week= c("Wednesday","Thursday","Wednesday","Thursday"),
       Category = c("ABC","FDE","ABC","FDE"),
       DR01 = c(4,1,2,3), DR02= c(4,2,0,2),DR03= c(9,5,0,1),
       DR04 = c(5,4,3,2),DR05 = c(5,4,0,2)),
  class = "data.frame", row.names = c(NA, -4L))
   
  dmda<-"2021-07-01"
    DTest <-"0"

df2<-df1%>%
group_by(Category,Week, DTT) %>%
summarize(across(starts_with("DR"), median),.groups = 'drop')

> df2
# A tibble: 3 x 8
  Category Week      DTT    DR01  DR02  DR03  DR04  DR05
  <chr>    <chr>     <chr> <dbl> <dbl> <dbl> <dbl> <dbl>
1 ABC      Wednesday Hol       3     2   4.5     4   2.5
2 FDE      Thursday  0         3     2   1       2   2  
3 FDE      Thursday  Hol       1     2   5       4   4

If I want to make an if condition I can do it like this:

if(any(df2$DTT == DTest & df2$Week == "Thursday" , na.rm = TRUE)) {
....
}

Now my doubt is that I didn't want to use df2$Week == "Thursday" but rather use dmda that was defined. In other words, is there any way, from the date I chose in dmda, for the code to identify what day of the week it is?

CodePudding user response：

We could convert the 'dmda' to Date class and extract the weekday with format (%A) - which is specified in the ?strptime documentation

%A - Full weekday name in the current locale. (Also matches abbreviated name on input.)

wkday <- format(as.Date(dmda), "%A")
wkday
[1] "Thursday"

and then use that in the if loop

if(any(df2$DTT == DTest & df2$Week == wkday , na.rm = TRUE)) {
....
}