R – Convert date to day-of-week in R

dater

I have a date in this format in my data frame:

"02-July-2015"

And I need to convert it to the day of the week (i.e. 183). Something like:

df$day_of_week <- weekdays(as.Date(df$date_column))

But this doesn't understand the format of the dates.

Best Answer

You could use lubridate to convert to day of week or day of year.

library(lubridate)

# "02-July-2015" is Thursday
date_string <- "02-July-2015"
dt <- dmy(date_string)
dt
## [1] "2015-07-02 UTC"

### Day of week : (1-7, Sunday is 1)
wday(dt)
## [1] 5

### Day of year (1-366; for 2015, only 365) 
yday(dt)
## [1] 183

### Or a little shorter to do the same thing for Day of year
yday(dmy("02-July-2015"))
## [1] 183

Related Solutions

Javascript – How to check whether an object is a date

As an alternative to duck typing via

typeof date.getMonth === 'function'

you can use the instanceof operator, i.e. But it will return true for invalid dates too, e.g. new Date('random_string') is also instance of Date

date instanceof Date

This will fail if objects are passed across frame boundaries.

A work-around for this is to check the object's class via

Object.prototype.toString.call(date) === '[object Date]'

Javascript – How to convert a JavaScript date to UTC

Simple and stupid

var date = new Date(); 
var now_utc =  Date.UTC(date.getUTCFullYear(), date.getUTCMonth(), date.getUTCDate(),
 date.getUTCHours(), date.getUTCMinutes(), date.getUTCSeconds());

 return new Date(now_utc);

Best Answer

Related Solutions

Javascript – How to check whether an object is a date

Javascript – How to convert a JavaScript date to UTC

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