Count the values of a column based on the values of another column in R

Using the dataframe I want to create a new one which will contain Zip, Name and a column named Count which will include the count of Name per Zip.

Zip<-c("123245","12345","123245","123456","123456","12345")
Name<-c("Bob","Bob","Bob","Jack","Jack","Mary"),
df<-data.frame(Zip,Name,Name2)

library(dplyr)
df %>%
  group_by(Zip) %>%
  mutate(Name = cumsum(Name))

expected

Zip Name Count
1 123245  Bob     2
2  12345  Bob     1
3  12345 Mary     1
4 123456 Jack     2

Does this solve your problem?

Zip<-c("123245","12345","123245","123456","123456","12345")
Name<-c("Bob","Bob","Bob","Jack","Jack","Mary")
df<-data.frame(Zip,Name)

library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union
df %>%
  group_by(Zip, Name) %>%
  summarise(Count = n())
#> `summarise()` has grouped output by 'Zip'. You can override using the `.groups` argument.
#> # A tibble: 4 × 3
#> # Groups:   Zip [3]
#>   Zip    Name  Count
#>   <chr>  <chr> <int>
#> 1 123245 Bob       2
#> 2 12345  Bob       1
#> 3 12345  Mary      1
#> 4 123456 Jack      2

^{Created on 2021-12-22 by the reprex package (v2.0.1)}

--

Quick speed benchmark:

library(tidyverse)
library(microbenchmark)

Zip<-c("123245","12345","123245","123456","123456","12345")
Name<-c("Bob","Bob","Bob","Jack","Jack","Mary")
df<-data.frame(Zip,Name)

JM <- function(df){
  df %>%
  group_by(Zip, Name) %>%
  summarise(Count = n())
}
JM(df)
#> `summarise()` has grouped output by 'Zip'. You can override using the `.groups` argument.
#> # A tibble: 4 × 3
#> # Groups:   Zip [3]
#>   Zip    Name  Count
#>   <chr>  <chr> <int>
#> 1 123245 Bob       2
#> 2 12345  Bob       1
#> 3 12345  Mary      1
#> 4 123456 Jack      2

TarJae <- function(df){
  df %>% 
    count(Zip, Name, name= "Count")
}

TIC <- function(df){
  aggregate(cbind(Count = Zip) ~ Zip + Name, df, length)
}
TIC(df)
#>      Zip Name Count
#> 1 123245  Bob     2
#> 2  12345  Bob     1
#> 3 123456 Jack     2
#> 4  12345 Mary     1

res <- microbenchmark(JM(df), TIC(df), TarJae(df))
autoplot(res)
#> Coordinate system already present. Adding new coordinate system, which will replace the existing one.

^{Created on 2021-12-22 by the reprex package (v2.0.1)}