Random option with different probability

Hello,

I'm looking for some help with something or maybe just a nudge in the right direction. Here's what I'm trying to do:

When player clicks certain item or icon I would like to give him 1 out of 4 options, but with different probability. For example, if a player clicks START MISSION, he would get one of 4 mission types (easy,normal,hard or very hard) but the chances would be 50% for easy,30%normal,20%hard and 10%very hard for instance. How would one accomplish something like this?

Thanks for any help

This will do just that, I set random range to be 1-indexed rather than 0-index so it's easier to see the percentage.

You could make a weighted random function by setting a string object.

0 = easy
1 = normal
2 = hard
3 = very hard

then populate it like: 00000111223 for example, and then set a value to val(Mid$( string$( "String" ), random(Len( string$( "String" ) )), 1)) to get a random number from the string.

Attachment 27166

a more robust approach is using a delimited string and the string tokenizer extension in the same fashion, only it allows you to use whole words or numbers with greater than 1 place (i.e 10). But for something simple this works good and is much faster than the list method others might recommend. You could alternatively use letters and numbers, and just set a second string to that same expression but without the val() conversion around it, then compare to the character you get for more options.

I turned it into an example i'll upload to the examples section: Attachment 27167

As it happens I was trying to figure out the same thing today, so I have a different method I can share. It's not as elegant and easy to tweak as @casleziro 's method, but it's contained in a single action, and is a lot faster due to not having to use strings (9 times faster, according to the profiler). If you only have to perform one or two of these in a frame, then I'd go with casleziro's method. But if you'll be performing 100 of these in a fastloop like I will, then this might be a good method, despite its crudeness.

This action will return a number between 1-5, with 1 being very common and 5 being very rare:

Set weightedRandomNumber to Max(1, RRandom( - 2, 1 ) + RRandom(0, 2) + RRandom(0, 2))

It's relatively self-explanatory, but basically what is happening is that it'll only be 5 if the blue and the green and the orange portions all output their highest numbers (1, 2, and 2, respectively). This will only happen rarely. It's more likely that a lower number will result. A result of 0, -1, or -2 (all of which are possible) will be forced to 1 by the max(1, at the start, which makes 1 a very likely outcome.

To get different ranges or probabilities, you can obviously change the numbers around or add/remove more rrandom() portions. But if you need to control your probabilities precisely to the last %, then I have no idea how you'd do that.

@Volnaiskra it's quite a bit more involved to get accurate percentage, but I was curious so I did it. Requires String Tokenizer extension (which is multiplatform!) and is most likely NOT fast due to loops and recursion. But it isn't slow enough to be noticeable at all. Maybe if you were working with a giant pool of items.

There are now 2 delimited strings you populate: item pool and item weights. The method sums together all the weights and picks a random number between 1 and the sum, then recursively loops through the list, subtracting the weight of each item from that picked number until it is lower or equal to 0. The loop breaks when this happens and returns the current item at loop index. Doesn't support float weights, but you don't really need them. Also supports duplicate weights, and the weights can be any number. The higher the weight the more common the item.

EDIT attached wrong file version

updated: Attachment 27171

@casleziro your second example (post #4) gave me an idea to do something similar, but using values, so it'd be cheaper. You just create an active object whose purpose is to hold a pool of numbers in its altVals, then you just choose one of those altVals at random:

numberPool : Set actualNumber to AltValN( "numberPool", RRandom(1, 15) )


http://bit.ly/2J6GCho

@Volnaiskra neat optimization! You get the added advantage of being able to use numbers greater than 1 place width.

With all the respect to all the previous answers, I would do it like this.

First, properly distribute your percentages. You can't have 50,30,20,10, cause the sum is 110%. That's not realistic. However you could do it if you want the odds to be 50 of 110, 30 of 110 etc.

But let's talk about a 100% sum. Let's distribute the difficulty levels:

1 - easy - 50%
2 - normal - 30%
3 - hard - 15%
4 - very hard -5%

50+30+15+5 = 100 so we are ok.

Now if you ask for a random number between 1 to 100, you can have the first 50 numbers be easy, the next 25 the normal etc. meaning:

1. 1-50 -> easy
2. 51-80 -> normal
3. 81-95 -> hard
4. 96-100 -> very hard

In order for this to work properly I have to assume that the random pick of fusion is indeed following the statistical rules (it is a true random with equal odds to pick any of the numbers).

Therefore the code is the following:
Attachment 27173

Here is the MFA if you want to test. - Attachment 27172

@AftPeakTank perfectly valid solution. I think it gets messy if you want many items, since fitting them all into 100 while also having decent weights is difficult. For something as small as the example, there's no reason you shouldn't use this method if you prefer.

a note though: reading from counters is slower than reading from an active's alterable value! I see counters used a lot around the forums so I figured I would mention it.

Quote:

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Originally Posted by casleziro

@AftPeakTank perfectly valid solution. I think it gets messy if you want many items, since fitting them all into 100 while also having decent weights is difficult. For something as small as the example, there's no reason you shouldn't use this method if you prefer.

a note though: reading from counters is slower than reading from an active's alterable value! I see counters used a lot around the forums so I figured I would mention it.

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@casleziro , I bet one can automate it to do as many weights you want. All you have to do is to use the sum of the odds instead of the 100% percentage.

It really is quite simple.

You do a random pick from 1 to "the sum of the odds" and you check with a loop so many times as the number of weights you want to have, to see in which range of numbers you are in. Then you apply your result.

By the way, I used the counter so one could see visualy how it works. This code can of course work in any type of values.

The sum method you're describing is similar to what I used in post #6.

Instead of comparing if you are in a range of numbers, the weight of each item is subtracted from the random pick from 1 to "sum of the odds" until it reaches 0. The loop is then broken and the current item returned. One comparison for each item is likely faster than multiple. But there are many ways to skin a cat, as the saying goes.

@Volnaiskra got me thinking of ways my method could be sped up even further. I think using an array with 2 y indexes (actual item and item weight) would be faster, or maybe 2 alterable value "containers" like he used in his optimization! Tokenizing a string is surely slow.

I didn't realize about the counters, sorry @AftPeakTank . I see them used a lot in examples and it irritates me much the same way the list object does X)

Quote:

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Originally Posted by casleziro

The sum method you're describing is similar to what I used in post #6.

Instead of comparing if you are in a range of numbers, the weight of each item is subtracted from the random pick from 1 to "sum of the odds" until it reaches 0. The loop is then broken and the current item returned. One comparison for each item is likely faster than multiple. But there are many ways to skin a cat, as the saying goes.

I didn't realize about the counters, sorry. I see them used a lot in examples and it irritates me much the same way the list object does X)

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Ahh, yes, like you said, looks like...But in the loop I wouldn't do it this way. I would just check for the range with a combo of conditions. I wouldn't loop so many times. Though even like you describe it would be fast enough. Fastloops are really fast.

Well, I see them too but they are only there for helping purposes...Aren't they?
hmmmm....
LOL
XD

@casleziro , here is the code I was describing.

I think it works. You can put as many weights as you want in the active object (works as a holder of values) and you need to update the first Alt. Value with the total number of weights.

Attachment 27175

Then the following events are doing the job:

Attachment 27174

You may download the MFA here Attachment 27176

Second frame holds the current example.

I think @Fenris is going to need a random number generator to decide which of the above methods to use X)

Quote:

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Originally Posted by Volnaiskra

I think @Fenris is going to need a random number generator to decide which of the above methods to use X)

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Now that was a good one...

@elvisish @Volnaiskra @AftPeakTank @casleziro
Thanks a ton guys! It's amazing to see how many different approaches there is. I guess I really need a random generator to decide which method to use :D
You've been extremely helpful, thank you very much

Quote:

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Originally Posted by AftPeakTank

@casleziro , here is the code I was describing.

I think it works. You can put as many weights as you want in the active object (works as a holder of values) and you need to update the first Alt. Value with the total number of weights.

Attachment 27175

Then the following events are doing the job:

Attachment 27174


Second frame holds the current example.

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Even though I will probably go with the simpler examples that will be more than enough for me, I really want to understand what is going in this one ;) Keep in mind, I'm a beginner to coding and fusion, and at this moment I have no idea what this example does :D I don't understand what the code does. It works like a charm, but I need to know how exactly. And I would really like to figure it out alone, because I think that'll be the best way to learn.

I have some business to do in the next two days, but when I get back home, I'll bury myself in this example and do my best to figure out what exactly it does and how. If I fail completely then I'd like to ask some more questions if that's ok :D If I don't reply in a week or two, then I probably figured it out and I thank you very much ;)

Quote:

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Originally Posted by Fenris

Even though I will probably go with the simpler examples that will be more than enough for me, I really want to understand what is going in this one ;) Keep in mind, I'm a beginner to coding and fusion, and at this moment I have no idea what this example does :D I don't understand what the code does. It works like a charm, but I need to know how exactly. And I would really like to figure it out alone, because I think that'll be the best way to learn.

I have some business to do in the next two days, but when I get back home, I'll bury myself in this example and do my best to figure out what exactly it does and how. If I fail completely then I'd like to ask some more questions if that's ok :D If I don't reply in a week or two, then I probably figured it out and I thank you very much ;)

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Ahh, happy I helped and you are satisfied. In fact the people in this community are always kind and help as much as possible.

Of course you may ask anything. Just tag me :)

Ok @AftPeakTank I finally figured it out. I'm kind of a math retard, so it took me more time than I'm willing to admit XD

I literally took pen and paper and went through the code multiple times to try to figure it out. And I did a rookie mistake thinking that LoopIndex is the number of loops and it gets smaller every time loop runs until I looked it up and learned that it actually goes up with every loop *facepalm*. I can't believe how simple it actually is :)

I just have one question. If i would set multiple values to 0, (because the options aren't available at the start of the game, for example) there shouldn't be any problems right? It would just add the 0 to the counter, 1 to LoopIndex and everything else would stay the same. I tried it a couple of times and it seems to work, i just want to make sure :)

Quote:

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Originally Posted by Fenris

Ok @AftPeakTank I finally figured it out. I'm kind of a math retard, so it took me more time than I'm willing to admit XD

I literally took pen and paper and went through the code multiple times to try to figure it out. And I did a rookie mistake thinking that LoopIndex is the number of loops and it gets smaller every time loop runs until I looked it up and learned that it actually goes up with every loop *facepalm*. I can't believe how simple it actually is :)

I just have one question. If i would set multiple values to 0, (because the options aren't available at the start of the game, for example) there shouldn't be any problems right? It would just add the 0 to the counter, 1 to LoopIndex and everything else would stay the same. I tried it a couple of times and it seems to work, i just want to make sure :)

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Excellent! I am happy for you. It is always so nice feeling to understand how things work.

Now hmm, let me think.... Normally it should be fine. I think it still works. You are right.