How do I randomly pick something from a table with raritys?
So I want to randomly pick different values from a table but with some rarer than others, how do I do this?
1 | local values = {"value1","value2","value3"} |
2 |
3 | local selectedvalue = math.random(1,#values) |
4 | --this works, but how do I do it if vaule 1 has twice as much change to be selected than value 2 and 3? This just gives them all the same chance... |
1
2 answers
One way of going about this is by duplicating the values in the table, like so:
1 | local values = {"value1","value1","value2","value3"} |
This way, however, can be long to type, so you could do something like this:
01 | -- For each entry, the first value is the actual value, and the second is the 'weight' or chance. |
02 | local values = { |
03 | {"value1", 2}, |
04 | {"value2", 1}, |
05 | {"value3", 1} |
06 | } |
07 |
08 | local SelectFrom = {} |
09 | local SelectedValue |
10 | for i, v in ipairs(values) do |
11 | for i2 = 1, v[2] do |
12 | table.insert(SelectFrom, v[1]) |
13 | end |
14 | SelectedValue = math.random(1, #SelectFrom) |
15 | end |
This works like the first method, but compresses the values, then decompresses them when selecting.
There may be other (better) ways; this is just the first one I came up with. It is also untested.
The first method is a pretty good one, and I'd go with that because it's the first one I thought of too. The alternative is to have a weight table, wherein the selection is done in part of a single random number out of 1.
01 | local items = { |
02 | {item1, 2}, |
03 | {item2, 3}, |
04 | {item3, 1}, |
05 | {item4, 1} |
06 | }; |
07 | local max = 0; |
08 | for i=1,#items do max = max+items[i][2] end; |
09 | local selection,cnt = math.random(),0; |
10 | for i=1,#items do |
11 | cnt = cnt+items[i][2]/max; |
12 | if cnt > selection then selection = items[i][1] break end; |
13 | end; |
14 | if type(selection) == 'number' then selection = items[#items][1] end --Just in case |
selection would at that point become your item. This is good because it can be mixed with other loot tables and have inheritance implemented with ease.