Number manipulation within Vim

Question

If I have a data file with columns of numbers like

3.14
0.42
6.66

Is there a way from within Vim that I can manipulate these with operations such as addition, subtraction and division? For instance, say I wanted to add 2.1 to each number in a column, how would I go about this? a

I can do it by piping to for instance awk, but I would like to know if there's a builtin method, and I haven't found anything in the help files.

Answer 1

Use CTRL-R with the expression register =.

The following command would add 2.1 to a number on a line:

C
<CTRL-R> =
<CTRL-R> "
+2.1
<ENTER>

Combine with macro it can yield some interesting results, such as this example.

Answer 2

Expression registers are great with vim.

Here is a more old fashioned vi way to doing this: Let us say you have a file containing a bunch of numbers one in each line and you want to add 2.1 to each of the lines.

:%s/$/+2.1/<ENTER> - this would append +2.1 to each line.
:1<ENTER>  - Goto the beginning of the file 
!Gbc<ENTER> - invoke the bc command on each line to do the addition.