Condition Effect Learning

This page reflects my idea about the Condition Effect Learning system. If you have comments, please dont delete text but add comments so I can reflect. See this as a first draft, which can be used as a basis for the Cheetah condition effect learning system.

As said in Advisory System, Cheetah needs a system that learns about the effect of certain conditions. As you can read in Advisory System, I think there are three kinds of conditions:

1. Certain conditions: the effect is known and fixed. The effect is fixed, so the learning system will see the effect as certain.
2. Uncertain conditions: the effect is not certain or not known yet. So, the effect is a prediction done by the system. The learning system tries to approve the prediction by looking at the past.

There are some comlications regarding learning about condition (e.g. food) effects. Since each human and each body is different, conditions dont always have a fixed certain effect. Food for instance has a GL (Glycamic Load) that tells about the effect of the food on BG (Blood Glucose) levels. Food effect (response) varies between individuals and between days as much as 20%. Likewise, effect of insulin and activities varies between people and temporally. Therefore, to account for intra-individual and temporal differences, I think it is a good thing to generally express condition effect by a range instead of a simple number. Such a range could be a probability distribution, or expressed as (minimum,maximum) tuple. For Cheetah, 'Learning' about conditions means assigning a range or distribution to it. There are several levels of expressing such variation in terms of a range or distribution. I solved the first one, but not yet the second.

1. Learning a condition's effect by assigning it a minimal and maximal effect value. For example, a minimum and maximum BG effect.
2. Learning a condition's effect by seeing it as a normally distributed random variable.

1. Learning a condition's effect by assigning it a minimal and maximal effect value

With this system, all conditions X have a X_hardmin and X_hardmax variables which tells the system the hard minimum and maximum of effect. For example, research has pointed out that a can of Coca-Cola has a Glycemic Load (GL) of minimally 14 and maximally 16. If we see the GL as the foods effect, we can assign CocaCola_hardmin=14 and CocaCola_hardmax=16. So, CocaCola could be a type 1 condition because it has a certain effect. When a user adds a new food type X to the database, it can add information like carbonhydrate(%), GI and such, to help the system determine X_hardmin and X_hardmax.

So, all conditions have a minimum and a maximum effect.
Suppose c is a condition, then:
<math>c_{min}, c_{max} \in \mathbb{R}</math>
<math>c_{min} \le c_{max}</math>

Also, conditions can be contained in a group (set) of conditions S:
S = {c1, c2, ...}
Like conditions, such group of conditions S also has minimum and maxmimum cumulative effect. Such effect is the sum of all of the effects of its contained conditions:
S_min = c1_min + c2_min + ...
S_max = c1_max + c2_max + ...

Using logics, set theory, intuition and commson sense, I came up with the following theorem. Lets call it Kingma's Theorem :). I havent formally proved it yet, but this seems to be true for all cases. Its actually quite logical.
if e is a port of set S (so S-e is set S minus condition c')
and S_min and S_max are known
and c_hardmin and c_hardmax are known
then can be said:
S-c_min = S_min - c_hardmax
S-c_max = S_max - c_hardmin

Lets assume that at each blood glucose (BG) measurement, Cheetah starts its learning system. Cheetah looks at all conditions that could have an effect, and puts all type 1 conditions into group CE (certain effect) and all type 2 into group UE (uncertain effect). Then, cheetah calculates the difference (min and max) between the BG_measurement and predicted CE group effect. This difference should equal the UE group effect. So:
BG_measurement = UE_real + CE_real
So:
UE_min = BG_measurement - CE_max
UE_max = BG_measurement - CE_min

UE is the range of the sum of the to be learned conditions. These conditions all have their own effect range, c_hardmin and c_hardmax. But because the sum of effects (UE) is restricted , each individual effect for each condition must be somewhat more restricted. The possible effect range for each effect can be deduced from the total effect and the hardmin and hardmax value of the other effects. Using Kingma's Theorem, one can deduce the effect range of each individual condition.

Example 1.1

Lets look at an example of how a system would learn. Say, the user adds a glucose mearurement entry and the system starts its learning system.

[Example is to be added]

2. Learning a condition's effect by seeing it as a normally distributed random variable

This is somewhat more complicated and needs to be mathematically worked out. One fact is that conditions can be seen as independent random variables that are normally distributed. This implies that the total effect of an arbitrarely large set of conditions can be easily computed as a Sum of normally distributed random variables. As quoted from wikipedia:

if

<math>X \sim N(\mu, \sigma^2)\,</math>

and

<math>Y \sim N(\nu, \tau^2)\,</math>

and X and Y are independent, then

<math>Z = X + Y \sim N(\mu + \nu, \sigma^2 + \tau^2).\,</math>