r - Sort a column and create a new one

Question

I have a data frame with a ID and date of diagnosis and date of procedure . There are many date of diagnosis and many procedure dates for the same ID. I want to create a new column called next date using the ID and the diagnosis date. for example my data looks like this

ID         Diagnosis date      Procedure date   Next Date
 1         2008-03-01           2009-04-05      2009-05-06
 1         2009-05-06           2008-03-02      2010-08-09
 1         2010-08-09           2015-08-09      2010-08-09
 1         2010-08-09           2013-07-08      2010-08-09
 2         2005-06-09           2009-09-02      2009-09-08
 2         2009-09-08           2010-06-05      2009-09-08

I want to get a separate column called Next Date based on Diagnosis date and sort the procedure date according to that. Because Procedure date should be after the diagnosis date.

Answer 1

assuming your data frame called 'data'

new <- data[order(as.Date(data$Diagnosis_Date, format="%Y-%m-%d")),]