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Introduction

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)

Method #8. Modifying the Datatype of a Column

Python

import pandas as pd

data = {'id': [1,2,3,4,5],
        'name': ['Jason', 'Jackie', 'Joe', 'Joshua', 'James']}
      
df = pd.DataFrame(data)

df.dtypes
id       int64
name    object
dtype: object

The id field is of integer type. Use astype() method to change it to string/character type as follows.

df2 = df.copy()
# change the id field to string/character type
df2['id'] = df2['id'].astype(str)
df2.dtypes
id      object
name    object
dtype: object

Sometimes we might have multiple columns to be transformed, this can be done super easily with astype().

# Sample DataFrame
data = {
    'col1': [1, 2, 3],
    'col2': [4, 5, 6],
    'col3': [7, 8, 9]
}

df3 = pd.DataFrame(data)

# Convert specific columns from numeric to string
columns_to_convert = ['col1', 'col2', 'col3']
df3[columns_to_convert] = df3[columns_to_convert].astype(str)

# Verify the data types
print(df3.dtypes)
col1    object
col2    object
col3    object
dtype: object

To change strings to numeric type, we could use astype(int), but this will throw an error when encountering non-numeric characters. Therefore, I prefer using pd.to_numeric() instead, which offers the errors parameter to determine how we want to handle non-numeric characters.

# Sample DataFrame
data = {
    'col1': ['1', 'Unknown', '3'],
    'col2': ['4', 'N.A.', '6'],
    'col3': ['7', '8', 'Missing']
}

df4 = pd.DataFrame(data)

# Using 'coerce': Non-numeric values will be converted to NaN
df4['col1'] = df4['col1'].apply(pd.to_numeric, errors='coerce')

# Using 'ignore': Non-numeric values will be left unchanged
df4['col2'] = df4['col2'].apply(pd.to_numeric, errors = 'ignore')

print(df4)
   col1  col2     col3
0   1.0     4        7
1   NaN  N.A.        8
2   3.0     6  Missing
print(df4.dtypes)
col1    float64
col2     object
col3     object
dtype: object
# Using 'raise': This will raise an error due to the presence of non-numeric values
try:
    df4['col3'] = pd.to_numeric(df4['col3'], errors='raise')
except ValueError as e:
    print("Error:", e)
Error: Unable to parse string "Missing" at position 2

R

# get the dataframe from python
df = py$df

library(dplyr)

df |>  glimpse()
Rows: 5
Columns: 2
$ id   <dbl> 1, 2, 3, 4, 5
$ name <chr> "Jason", "Jackie", "Joe", "Joshua", "James"

Use the as.character() function to change the id field into string/character type, and use as.numeric() function to change it back to numeric. (id: what did I do? :p)

# change the id field to string/character type
df = df |> mutate(id = as.character(id))
df |>  glimpse()
Rows: 5
Columns: 2
$ id   <chr> "1", "2", "3", "4", "5"
$ name <chr> "Jason", "Jackie", "Joe", "Joshua", "James"
# change the id field back to numeric type
df = df |> mutate(id = as.numeric(id))
df |> glimpse()
Rows: 5
Columns: 2
$ id   <dbl> 1, 2, 3, 4, 5
$ name <chr> "Jason", "Jackie", "Joe", "Joshua", "James"

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