How to Remove Dollar Sign in R (and other currency symbols)

Let’s say we imported a .csv or .xlsx file into R, and it’s like this:

print(df)

    person payment
1 Person 1  $56.11
2 Person 2  $20.42
3 Person 3 $104.20
4 Person 4 $201.21
5 Person 5   $5.06

Looks fine, until you try to do a calculation on the payment column:

sum(df$payment]

Error in sum(df$payment) : invalid 'type' (character) of argument

So we run str(df) to check the table structure. Lo and behold, that column is not a numeric variable, it is character (chr):

'data.frame':	5 obs. of  2 variables:
 $ person : chr  "Person 1" "Person 2" "Person 3" "Person 4" ...
 $ payment: chr  "$56.11" "$20.42" "$104.20" "$201.21" ...

How to remove the dollar signs from column in R

One way to do it is with the gsub() function, in conjunction with as.numeric(). gsub() is used to substitute specific text from a string with other text, and as.numeric() can coerce a variable to numeric.

Let’ see it in action:

# replace $ with blank "" in the df$payment column.  and coerce that result to numeric
df$payment_2 = as.numeric(gsub("\\$", "", df$payment))

# print the data frame just to eyeball it
df

# compute sum of payment_2 column
sum(df$payment_2)

The gsub() function looks for any instance of “\$” and replaces it with “”. The forward-slashes are known as escape characters. They are needed because gsub() accepts “regular expression” as the first parameter, and since $ is a reserved regular expression notation, we must “escape” this reserved meaning and look for literal values of $ in the text strings.

    person payment payment_2
1 Person 1  $56.11     56.11
2 Person 2  $20.42     20.42
3 Person 3 $104.20    104.20
4 Person 4 $201.21    201.21
5 Person 5   $5.06      5.06

[1] 387

By the same token, we can replace commas and other currency-related notations that are being read as part of the string. We can do them individual as we did above with the dollar sign, or we can specify any number of symbols to remove, all at once. For example, to remove both dollar sign and comma, we use the following notation:

# replace $ and comma with blank "" in the df$payment column
df$payment_2 = as.numeric(gsub("[\\$,]", "", df$payment))

Here we modified the gsub() function to include [\\$,]. We could add any number of other symbols within brackets that we wish to replace.

And don’t forget. We just used data frame columns for convenience here. But a column is simply a vector, so generically speaking, this approach can be used for any kind of vector.