How to use the 'sweep' function

Question

When I look at the source of R Packages, i see the function sweep used quite often. Sometimes it\'s used when a simpler function would have sufficed (e.g.,

Answer 1

sweep() is typically used when you operate a matrix by row or by column, and the other input of the operation is a different value for each row / column. Whether you operate by row or column is defined by MARGIN, as for apply(). The values used for what I called "the other input" is defined by STATS. So, for each row (or column), you will take a value from STATS and use in the operation defined by FUN.

For instance, if you want to add 1 to the 1st row, 2 to the 2nd, etc. of the matrix you defined, you will do:

sweep (M, 1, c(1: 4), "+")

I frankly did not understand the definition in the R documentation either, I just learned by looking up examples.