如何从不同的行收集信息？

Question

library(data.table)
#This is the raw dataframe
(dt <- data.table(name=c('Tom','Tom','Tom','Jake','Jake','Jake'),
                 math=c(NA,70,NA,45,NA,NA),
                 music=c(20,NA,NA,NA,NA,65),
                 english=c(NA,NA,85,NA,30,NA)))
#>    name math music english
#> 1:  Tom   NA    20      NA
#> 2:  Tom   70    NA      NA
#> 3:  Tom   NA    NA      85
#> 4: Jake   45    NA      NA
#> 5: Jake   NA    NA      30
#> 6: Jake   NA    65      NA
# This is target dataframe
(target_dt <- data.table(name=c('Tom','Jake'),
                        math=c(70,45),
                        music=c(20,65),
                        english=c(85,30)))
#>    name math music english
#> 1:  Tom   70    20      85
#> 2: Jake   45    65      30

由reprex package（v0.2.0）于2018-09-06创建。

有没有简单的方法可以做到这一点？