R - Adding numbers within a data frame cell together

Question

I have a data frame in which the values are stored as characters. However, many values contain two numbers that need to be added together. Example:

                    2014 Q1 Sales   2014 Q2 Sales   2014 Q3 Sales   2014 Q4 Sales 
  Product 1                  3+6            2+10               8            13+2
  Product 2                    6             4+0            <NA>               5
  Product 3                 <NA>             5+9             3+1              11

Is there a way to go through the whole data frame and replace all cells containing characters like "3+6" with new values equal to their sum? I assume this would involve coercing the characters to numeric or integers, but I don't know how that would be possible for values with the + sign in them. I would like the example data frame to end up looking like this:

                    2014 Q1 Sales   2014 Q2 Sales   2014 Q3 Sales   2014 Q4 Sales 
  Product 1                    9              12               8              15
  Product 2                    6               4            <NA>               5
  Product 3                 <NA>              14               4              11

Answer 1

Here's an easier example:

dat <- data.frame(a=c("3+6", "10"), b=c("12", NA), c=c("3+4", "5+6"))
dat
##      a    b   c
##  1 3+6   12 3+4
##  2  10 <NA> 5+6

apply(dat, 1:2, function(x) eval(parse(text=x)))
##       a  b  c
## [1,]  9 12  7
## [2,] 10 NA 11

Using R itself to do the computation with eval and parse does the trick.