/
bayes.go
140 lines (130 loc) · 3.67 KB
/
bayes.go
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// Copyright 2021 Silvio Böhler
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package bayes
import (
"math"
"strings"
"github.com/sboehler/knut/lib/journal"
"github.com/sboehler/knut/lib/journal/ast"
)
// Model is a model trained from a journal
type Model struct {
accounts int
accountCounts map[*journal.Account]int
tokenCounts map[string]map[*journal.Account]int
exclude *journal.Account
}
// NewModel creates a new model.
func NewModel(exclude *journal.Account) *Model {
return &Model{
accounts: 0,
accountCounts: make(map[*journal.Account]int),
tokenCounts: make(map[string]map[*journal.Account]int),
}
}
// Update updates the model with the given transaction.
func (m *Model) Update(t *ast.Transaction) {
for _, p := range t.Postings() {
if p.Credit != m.exclude {
m.accounts++
m.accountCounts[p.Credit]++
for token := range tokenize(t.Description(), &p, p.Credit) {
tc, ok := m.tokenCounts[token]
if !ok {
tc = make(map[*journal.Account]int)
m.tokenCounts[token] = tc
}
tc[p.Credit]++
}
}
if p.Debit != m.exclude {
m.accounts++
m.accountCounts[p.Debit]++
for token := range tokenize(t.Description(), &p, p.Debit) {
tc, ok := m.tokenCounts[token]
if !ok {
tc = make(map[*journal.Account]int)
m.tokenCounts[token] = tc
}
tc[p.Debit]++
}
}
}
}
// Infer replaces the given account with an inferred account.
func (m *Model) Infer(t *ast.Transaction, tbd *journal.Account) *ast.Transaction {
trx := t.ToBuilder()
for i := range trx.Postings {
var (
posting = &trx.Postings[i]
tokens map[string]struct{}
)
switch tbd {
case posting.Credit, posting.Debit:
tokens = tokenize(t.Description(), posting, tbd)
case posting.Debit:
tokens = tokenize(t.Description(), posting, tbd)
default:
continue
}
scores := make(map[*journal.Account]float64)
for a, accountCount := range m.accountCounts {
if a == tbd {
continue
}
scores[a] = math.Log(float64(accountCount) / float64(m.accounts))
for token := range tokens {
if tokenCount, ok := m.tokenCounts[token][a]; ok {
scores[a] += math.Log(float64(tokenCount) / float64(accountCount))
} else {
// assign a low but positive default probability
scores[a] += math.Log(1.0 / float64(m.accounts))
}
}
}
var (
selected *journal.Account
max = math.Inf(-1)
)
for a, score := range scores {
if score > max && a != posting.Credit && a != posting.Debit {
selected = a
max = score
}
}
if selected != nil {
if posting.Credit == tbd {
posting.Credit = selected
}
if posting.Debit == tbd {
posting.Debit = selected
}
}
}
return trx.Build()
}
func tokenize(desc string, posting *ast.Posting, account *journal.Account) map[string]struct{} {
tokens := append(strings.Fields(desc), posting.Commodity.String(), posting.Amount.String())
if account == posting.Credit {
tokens = append(tokens, "credit", posting.Debit.String())
}
if account == posting.Debit {
tokens = append(tokens, "debit", posting.Credit.String())
}
result := make(map[string]struct{})
for _, token := range tokens {
result[strings.ToLower(token)] = struct{}{}
}
return result
}