Last updated: 2022-11-12

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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 #11. Filling NaN values

Python

We can use the df.fillna() method to replace missing values with a specific value. Let’s start by creating a dataframe with missing values.

import pandas as pd
import numpy as np

df = pd.DataFrame({'col1': [1,2],
                   'col2': [3,np.nan],
                   'col3': ['A',np.nan]})
print(df)
   col1  col2 col3
0     1   3.0    A
1     2   NaN  NaN

To replace the missing value with 0, just do .fillna(0).

# replace all NA values with 0, inplace = True means df itself will be modefied
df.fillna(0, inplace = True)
print(df)
   col1  col2 col3
0     1   3.0    A
1     2   0.0    0

Or if you only wnat to replace missing values in one particular column, simply select it first

df2 = df.copy()
df2['col2'].fillna(0, inplace = True) 
print(df2)
   col1  col2 col3
0     1   3.0    A
1     2   0.0    0

R

We can use either replace() in base R to replace all missings in a dataframe with a specific value, or replace_na in tidyr to offer tailored replacement for each specific column.

df = data.frame(col1 = c(1,2),
                col2 = c(3, NA),
                col3 = c('A',NA))

print(df)
  col1 col2 col3
1    1    3    A
2    2   NA <NA>
# use replace() in base R to replace all missings to 0
replace(df, is.na(df), 0)
  col1 col2 col3
1    1    3    A
2    2    0    0
library(tidyr)
# or use replace_na() in tidyverse to offer tailored replacement for each column. 
df |>  replace_na(list(col2=0,col3="Unknown"))
  col1 col2    col3
1    1    3       A
2    2    0 Unknown

sessionInfo()
R version 4.2.1 (2022-06-23 ucrt)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 19043)

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] tidyr_1.2.1     reticulate_1.26

loaded via a namespace (and not attached):
 [1] Rcpp_1.0.9       pillar_1.8.1     compiler_4.2.1   bslib_0.4.0     
 [5] later_1.3.0      jquerylib_0.1.4  git2r_0.30.1     workflowr_1.7.0 
 [9] tools_4.2.1      digest_0.6.29    lattice_0.20-45  jsonlite_1.8.2  
[13] evaluate_0.17    lifecycle_1.0.3  tibble_3.1.8     png_0.1-7       
[17] pkgconfig_2.0.3  rlang_1.0.6      Matrix_1.4-1     DBI_1.1.3       
[21] cli_3.4.1        rstudioapi_0.14  yaml_2.3.5       xfun_0.33       
[25] fastmap_1.1.0    dplyr_1.0.10     stringr_1.4.1    knitr_1.40      
[29] generics_0.1.3   fs_1.5.2         vctrs_0.4.2      sass_0.4.2      
[33] tidyselect_1.2.0 grid_4.2.1       rprojroot_2.0.3  glue_1.6.2      
[37] R6_2.5.1         fansi_1.0.3      rmarkdown_2.17   purrr_0.3.5     
[41] magrittr_2.0.3   whisker_0.4      ellipsis_0.3.2   promises_1.2.0.1
[45] htmltools_0.5.3  assertthat_0.2.1 renv_0.16.0      httpuv_1.6.6    
[49] utf8_1.2.2       stringi_1.7.8    cachem_1.0.6