R: spread function on data frame with duplicates

Question

I have a data frame that I need to pivot but the data frame has duplicate identifiers, so spread function gives an error Error: Duplicate identifiers for

Answer 1

You could use dcast from the devel version of data.table ie. v1.9.5. Instructions to install are here

library(data.table)#v1.9.5+
dcast(setDT(df), Dimension~Date, value.var='Metric', 
               fun.aggregate=function(x) toString(unique(x)))
#   Dimension  Fri Mon Tue Wed
#1:         A 7, 8  23  25    
#2:         B        7       9

Or

library(dplyr)
library(tidyr)
df %>%
   group_by(Dimension, Date) %>% 
   summarise(Metric=toString(unique(Metric))) %>% 
   spread(Date, Metric, fill='')
#   Dimension  Fri Mon Tue Wed
#1         A 7, 8  23  25    
#2         B        7       9

Update

Using the new dataset from `OP's post

 setDF(df2)
 df2 %>% 
     group_by(Dimension, Date) %>% 
     summarise(Metric=toString(unique(Metric))) %>%
     spread(Date, Metric, fill='') %>%
     head(2) %>%
     select(1:3)
 #    Dimension 16 analog tuner
 #1 10994030020  9             
 #2 12300245685            NTSC