[Solved] How adjust code functionality to specifications using data.table function

by


With data.table, we can specify the .SDcols to select the ‘DR’ columns or ‘date_cols’ and assign back the output to those, then instead of using rowwise matching, use a row/column indexing to extract the values to create the ‘Result’

library(data.table)
# get the column names that starts with DR
dr_names <- grep("^DR", names(df1), value = TRUE)
# get the columns that contains date as substring
date_names <- grep("date", names(df1), value = TRUE)
# setDT - converts the data.frame to data.table
# .SDcols - specify the dr_names, date_names, loop over those
# with lapply, apply the functions and assign (`:=`) back to 
# same columns
setDT(df1)[, (dr_names) := lapply(.SD, function(x) coef - x), .SDcols = dr_names
    ][, (date_names) := lapply(.SD, as.IDate), .SDcols = date_names
    ][, datedif := date2 - date1]
# rename with setnames
setnames(df1, dr_names, sub("([A-Z])0+", "\\1", dr_names))

# Extract the corresponding 'DRM' column based on the value from 
# datediff and match it with the DRM column names
# using a row/column indexing 
# return the Result and coef columns 
Output2 <- df1[,  .(coef, Result = as.matrix(.SD)[cbind(.I, 
       match(paste0('DRM', datedif), names(.SD)))]), 
     .SDcols = patterns("^DRM\\d+")]
Output2[is.na(Result), Result := coef]

-output

> Output2
    coef Result
   <num>  <num>
1:     8      6

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solved How adjust code functionality to specifications using data.table function