example using mutate_at() and base R to edit multiple columns indexed from another data frame

mutate_at_base_R_example.R

# load in packages
library(dplyr)

# create two random dataframes
random <- data.frame(y = rnorm(30, 10), x = rnorm(30, 100), z = rnorm(30, -15))
fixed <- data.frame(y = rnorm(30, 10), x = rnorm(30, 10), z = rnorm(30, 10), a = rnorm(30, 10))

# find columns to change the values of
cols_change <- colnames(fixed)[colnames(fixed) %in% colnames(random)]

# change the value of fixed based on the corresponding column in random ####

# tidyverse
fixed %>% mutate_at(vars(cols_change), funs(. + random$.)) -> fixed2
fixed2

# base R
fixed[names(random)] <- random + fixed[names(random)]
fixed