Replacing occurrences of a number in multiple columns of data frame with another value in R

Question

ETA: the point of the below, by the way, is to not have to iterate through my entire set of column vectors, just in case that was a proposed solution (just

Answer 1

Just to provide a different answer, I thought I would write up a vector-math approach:

You can create a transformation matrix (really a data frame here, but will work the same), using a the vectorized 'ifelse' statement and multiply the transformation matrix and your original data, like so:

df.Rep <- function(.data_Frame, .search_Columns, .search_Value, .sub_Value){
   .data_Frame[, .search_Columns] <- ifelse(.data_Frame[, .search_Columns]==.search_Value,.sub_Value/.search_Value,1) * .data_Frame[, .search_Columns]
    return(.data_Frame)
}

To replace all values 4 with 10 in the data frame 'data' in columns 2 through 3, you would use the function like so:

# Either of these will work.  I'm just showing options.
df.Rep(data, 2:3, 4, 10)
df.Rep(data, c("var1","var2"), 4, 10)

#   name var1 var2
# 1    a    1    3
# 2    a    2    3
# 3    a    3    3
# 4    b   10   10
# 5    b    5   10
# 6    b    6   10
# 7    c    7    5
# 8    c    8    5
# 9    c    9    5