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Introduction

Provide a Python to R translation of 30 essential Pandas methods introduced by Avi Chawla in The Only 30 Methods You Should Master To Become A Pandas Pro published on TowardsDataScience.

Set up

# enable python in RMarkdown
library(reticulate)

Create the dataframe in Python

import pandas as pd

df = pd.DataFrame([[6, 5,  10], 
                   [5, 8,  6], 
                   [5, 10, 6], 
                   [4, 7,  10]],
                  columns = ["Maths", "Science", "English"])

print(df)

   Maths  Science  English
0      6        5       10
1      5        8        6
2      5       10        6
3      4        7       10

Load the dataframe into R

df <- py$df #access df as saved in Python(py) above

print(df)

  Maths Science English
1     6       5      10
2     5       8       6
3     5      10       6
4     4       7      10

Method #22-23. Finding Unique Values in a DataFrame

Python

use unique() to find unique values, and nunique() for the number of unique values

df['Maths'].unique() # get unique values in the 'Maths' column

array([6, 5, 4], dtype=int64)

df['English'].unique() # get unique values in the 'English' column

array([10,  6], dtype=int64)

df['Maths'].nunique() # get the number of unique values in the 'Maths' column

df['English'].nunique() # get the number of unique values in the 'English' column

R

To get unique values of a column, we select the column then apply the unique() function. This can also be used to find unique value combinations across multiple variables. To count the number of unique values or value combinations, just apply length() function to count its length.

For python, unique() can’t be used to get unique value combinations across multiple variables. If this is what you seek to do, please refer to method 26 in Avi’s article which we will get to translate soon.

library(dplyr)

# unique values in one single column
df |> 
  select(Maths) |> 
  unique()

# unique combination of values across multiple columns
df |> 
  select(Maths, English) |> 
  unique()

  Maths English
1     6      10
2     5       6
4     4      10

# count the number of unique values or value combination
df |> 
  select(Maths, English) |> 
  unique() |> 
  length()

[1] 2

sessionInfo()

R version 4.2.1 (2022-06-23 ucrt)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 19045)

Matrix products: default

locale:
[1] LC_COLLATE=English_Australia.utf8  LC_CTYPE=English_Australia.utf8   
[3] LC_MONETARY=English_Australia.utf8 LC_NUMERIC=C                      
[5] LC_TIME=English_Australia.utf8    

attached base packages:
[1] stats     graphics  grDevices datasets  utils     methods   base     

other attached packages:
[1] dplyr_1.1.2     reticulate_1.30

loaded via a namespace (and not attached):
 [1] Rcpp_1.0.11       pillar_1.9.0      compiler_4.2.1    bslib_0.5.0      
 [5] later_1.3.1       jquerylib_0.1.4   git2r_0.32.0      workflowr_1.7.0  
 [9] tools_4.2.1       digest_0.6.33     lattice_0.20-45   jsonlite_1.8.7   
[13] evaluate_0.21     lifecycle_1.0.3   tibble_3.2.1      png_0.1-8        
[17] pkgconfig_2.0.3   rlang_1.1.1       Matrix_1.4-1      cli_3.6.1        
[21] rstudioapi_0.15.0 yaml_2.3.7        xfun_0.39         fastmap_1.1.1    
[25] withr_2.5.0       stringr_1.5.0     knitr_1.43        generics_0.1.3   
[29] fs_1.6.2          vctrs_0.6.3       sass_0.4.7        tidyselect_1.2.0 
[33] grid_4.2.1        rprojroot_2.0.3   glue_1.6.2        R6_2.5.1         
[37] fansi_1.0.4       rmarkdown_2.23    magrittr_2.0.3    whisker_0.4.1    
[41] promises_1.2.0.1  htmltools_0.5.5   renv_1.0.0        httpuv_1.6.11    
[45] utf8_1.2.3        stringi_1.7.12    cachem_1.0.8

Method #22-23 Finding Unique Values in a DataFrame

Python to R Translation of 30 Essential Pandas Methods

Mena WANG

2022-11-17