Talk:Functional coverage tree: Difference between revisions
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(→Data in a more functional form: Weighted sums.) |
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I did not use the above, but thought I should generate it. --[[User:Paddy3118|Paddy3118]] ([[User talk:Paddy3118|talk]]) 20:02, 12 August 2015 (UTC) |
I did not use the above, but thought I should generate it. --[[User:Paddy3118|Paddy3118]] ([[User talk:Paddy3118|talk]]) 20:02, 12 August 2015 (UTC) |
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===Weighted sums=== |
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The specified weights look like they are meant to be percentages (all=100), but the specification for missing weights seems to be fractional (all=1). I think that this deserves either a bit more explanation (as to why the use of "1" for default weight is correct) or correction. --[[User:Rdm|Rdm]] ([[User talk:Rdm|talk]]) 01:53, 13 August 2015 (UTC) |
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:Hi Rdm, Those weights are not percentages - They are "fractions of the sum of the weights" at that level. I was playing around with what weight to apply to house1 and house2 and rejected 1, 2 then eventually considered 2, 3 and realised that for those integers it would be the same as 5, 6 and 40, 60 - saw the total weight of being 100 and the |
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:# Ease of hand calculation. |
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:# Similarity to prcentages. |
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:And so went with that. Never thinking that it might confuse rather than help. |
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:Here are some doodles around the weighted average calculation: |
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:<lang python>>>> def wt_avg(wt, cov): |
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... wts = sum(wt) |
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... covs = sum(c * w for c, w in zip(cov, wt)) |
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... return covs / wts |
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... |
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>>> weights = [1, 1] |
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>>> child_cov = [0.5, 0.5] |
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>>> wt_avg(weights, child_cov) |
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0.5 |
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>>> weights = [2, 3] |
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>>> wt_avg(weights, child_cov) |
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0.5 |
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>>> weights = [1, 1] |
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>>> child_cov = [0.25, 0.75] |
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>>> wt_avg(weights, child_cov) |
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0.5 |
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>>> weights = [2, 3] |
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>>> wt_avg(weights, child_cov) |
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0.55 |
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>>> weights = [4, 6] |
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>>> wt_avg(weights, child_cov) |
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0.55 |
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>>> weights = [40, 60] |
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>>> wt_avg(weights, child_cov) |
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0.55 |
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>>> |
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>>> # From wikipedias basic example: |
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>>> weights = [20, 30] |
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>>> child_cov = [80, 90] |
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>>> wt_avg(weights, child_cov) |
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86.0 |
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>>> </lang> |
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