[R] Date format

[Bert Gunter]

$date is a factor, which is coded as numeric values internally, which
as.date sees as numeric, and therefore:
"as.Date will accept numeric data (the number of days since an epoch),
but only if origin is supplied." (from ?as.Date)

You need to supply a format argument to as.Date to get it to handle
the factor properly; e.g.
"%d.%m.%Y"  should work. See ?strptime for formatting details.

Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

On Sat, May 9, 2020 at 5:31 PM Medic <mailiPadpost using gmail.com> wrote:
>
> I took a SAMPLE CODE (for Connected scatterplot) from the R gallery
> and applied to MY DATA, but got:
> "Error in as.Date.numeric(mydata$date) : 'origin' must be supplied".
> P.S. I can not understand ?as.Date()
>
> SAMPLE CODE
> library(ggplot2)
> library(dplyr)
> library(hrbrthemes)
> data <- read.table("https://raw.githubusercontent.com/holtzy/data_to_viz/master/Example_dataset/3_TwoNumOrdered.csv",
> header=T)
>
> str(data)
> 'data.frame': 1822 obs. of  2 variables:
>  $ date : chr  "2013-04-28" "2013-04-29" "2013-04-30" "2013-05-01" ...
>  $ value: num  136 147 147 140 126 ...
>
> data$date <- as.Date(data$date)
>
> # Plot
> data %>%
>   tail(10) %>%
>   ggplot( aes(x=date, y=value)) +
>     geom_line( color="grey") +
>     geom_point(shape=21, color="black", fill="#69b3a2", size=6) +
>     theme_ipsum() +
>     ggtitle("Evolution of bitcoin price")
>
>
> MY DATA
> mydata <- read.table("E:/mydata.csv", header=TRUE, sep=";", dec=",")
>
> str(mydata)
> 'data.frame': 7 obs. of  2 variables:
>  $ date : chr  "01.01.2000" "02.01.2000" "03.01.2000" "04.01.2000" ...
>  $ value: int  11 12 13 14 15 16 17
>
> mydata$date <- as.Date(mydata$date)
> Error in as.Date.numeric(mydata$date) : 'origin' must be supplied
>
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