将dataframe1转换为dataframe2，其中列的值成为新列

Question

I am working with dataframes in R and I would like to change the format of table 1 (image1), to the table 2 (image2).

I know that i have 50 'City' possible values, from 1 to 50. What i want is that those values of 'City' become different columns, so below each of these values the number of 'House' is shown. Finally i would have only one row for every Country, and 52 columns. ('Number','Country',1,2,3...,50). (This is a simplify version, the main one has much more values of 'Number', so i am looking for a solution that works 'fast', that does not take long for running)

Answer 1

If df is your dataframe and columns are lowercase the following dplyr::pivot_wider will help you.

library(dplyr)
df %>% 
  pivot_wider(id_cols=c(number,country),names_from=city,values_from=house)

To give you this output.

# A tibble: 3 × 7
  number country `21`  `23`  `24`  `22`  `25` 
   <int>   <int> <chr> <chr> <chr> <chr> <chr>
1   6205       2 2     a     5     NA    NA   
2   6205       3 NA    5     5     1     5    
3   6205       4 4     2     7     3     2    
> 

Its advisable to not use numeric dataframe column names, hence ideal to re-look at your naming conventions.