Substitute figure by math

Question

I have a file like this:

1 2 3  
4 5 6  
7 8 9  
0 1 2  

I want to change a block-wise visual selection area, e.g. 5 and 8. I want to substitute them by multiplying the figures by 0.7 and I want to round to 3 digits, e.g. 5 changed to 3.500.

I know submatch can work the math, but I don’t know how to define the grouped part.

Answer 1

You could try this:

:'<,'>s/\%V\d*\%V\d/\=printf('%.3f', str2nr(submatch(0))*0.7)/

For more info, see:

• :h /\%V
• :h printf()

---

Figure could be 5, 5.0, 5.00 or 5.000, 12345678.000, 3 digits at most. How can we define a more general grouped part?

Try a more permissive pattern:

:'<,'>s/\%V\d*\.\=\d*\%V\d/\=printf('%.3f', str2float(submatch(0))*0.7)/

Answer 2

Visual Block: Colon commands will still apply to whole lines

You find in the user manual section 10.3 'Command ranges' following note (almost at the end of :h 10.3:

Note: When using Visual mode to select part of a line, or using CTRL-V to select a block of text, the colon commands will still apply to whole lines. This might change in a future version of Vim.

A substitute command operating on the whole line would look like

:'<,'>s/\(\d*\s*\)\(\d*\)\(\s*.*\)/\=printf('%d %.3f %d', submatch(1), str2nr(submatch(2))*0.7, submatch(3))

Alternative, filter lines through awk:

:'<,'>!awk '{printf "\%d \%.3f \%d\n", $1, $2*0.7, $3}'

\%V

Please note the answer by @user938271 using the special atom \%V in a pattern. This circumvents the limitation that colon commands work always on whole lines for the :substitute command.

Answer 3

:B from plugin vis.vim by DrChip: :B s/pattern/becomes/

This plugin provides a general command to make all colon commands to operate only on the visual block selection:

:'<,'>B s/\d*/\=printf('%.3f', str2nr(submatch(0))*0.7)

Answer 4

:Substitute for visual block from plugin csv.vim

For single-space separated data you have to initialize the plugin csv.vim manually as following:

$ vim mydata
:setf csv
:let g:csv_delim=' '
:CSVInit

Now you can use the :Substitute command:

Select part of a column with a visual block (e.g. 5\n8) and then run

:'<,'>Substitute \d*/\=printf('%.3f', str2nr(submatch(0))*0.7)