How to change column name according to another dataframe in R?

Question

df1 <- data.frame(
    cola = c('1',NA,'c','1','1','e','1',NA,'c','d'),
    colb = c("A",NA,"C","D",'a','b','c','d','c','d'),
    colc = c('a',NA,'c','d','a',NA,'c',NA,'c','d'),stringsAsFactors = TRUE)

df2<-data.frame(name=c('cola','colc','colb'),
                altname=c('a','c','b'))

df1 %>% table %>% data.frame(.)

Result of above codes as:

   cola colb colc Freq
1     1    a    a    1
2     c    a    a    0

I want to change columns name of result based on df2(for example,change colb to b ),the expected result as:

      a    b    c Freq
1     1    a    a    1
2     c    a    a    0

How to do it?

Answer 1

We can just remove the substring with rename_at

library(stringr)
libraryr(dplyr)
df1 %>% 
   table %>% 
   data.frame(.) %>%  
   rename_at(1:3, ~ str_remove(., "col"))

Or if it needs to be from 'df2'

df1 %>%
   table %>%
   data.frame(.) %>%
   rename_at(1:3, ~ setNames(as.character(df2$altname), df2$name)[.])

Update

If all the column names in 'df1' are not in key/val columns of 'df2', an option is

df1 %>%
   table %>%
    data.frame(.) %>%
    rename_at(1:3, ~ coalesce(setNames(as.character(df2$altname), df2$name)[.], .)) 

---

Or using base R

out <- df1 %>% table %>% data.frame(.)
names(out) <- sub("col", "", names(out))

if it needs to be based on a second dataset

name(out)[-4] <- df2$altname[match(names(out)[-4], df2$name)]

Or with substr

names(out) <- substring(names(out), 4)