StringDistances.jl/src/compare.jl

255 lines
8.5 KiB
Julia
Executable File

"""
compare(s1::AbstractString, s2::AbstractString, dist::StringDistance)
return a similarity score between 0 and 1 for the strings `s1` and
`s2` based on the `StringDistance` `dist`
### Examples
```julia-repl
julia> compare("martha", "marhta", Levenshtein())
0.6666666666666667
```
"""
function compare(s1::AbstractString, s2::AbstractString,
dist::Union{Jaro, RatcliffObershelp}; min_score = 0.0)
1.0 - evaluate(dist, s1, s2)
end
function compare(s1::AbstractString, s2::AbstractString,
dist::Union{Levenshtein, DamerauLevenshtein}; min_score = 0.0)
s1, s2 = reorder(s1, s2)
len1, len2 = length(s1), length(s2)
len2 == 0 && return 1.0
if min_score == 0.0
return 1.0 - evaluate(dist, s1, s2) / len2
else
d = evaluate(dist, s1, s2; max_dist = ceil(Int, len2 * (1 - min_score)))
out = 1.0 - d / len2
out < min_score && return 0.0
return out
end
end
function compare(s1::AbstractString, s2::AbstractString,
dist::QGramDistance; min_score = 0.0)
# When string length < q for qgram distance, returns s1 == s2
s1, s2 = reorder(s1, s2)
len1, len2 = length(s1), length(s2)
len1 <= dist.q - 1 && return convert(Float64, s1 == s2)
if typeof(dist) <: QGram
1.0 - evaluate(dist, s1, s2) / (len1 + len2 - 2 * dist.q + 2)
else
1.0 - evaluate(dist, s1, s2)
end
end
"""
Winkler(dist::StringDistance; p::Real = 0.1, threshold::Real = 0.7, maxlength::Integer = 4)
Creates the `Winkler{dist, p, threshold, maxlength}` distance
`Winkler{dist, p, threshold, length)` modifies the string distance `dist` to boost the
similarity score between two strings, when their original similarity score is above some `threshold`.
The boost is equal to `min(l, maxlength) * p * (1 - score)` where `l` denotes the
length of their common prefix and `score` denotes the original score
"""
struct Winkler{S <: StringDistance} <: StringDistance
dist::S
p::Float64 # scaling factor. Default to 0.1
threshold::Float64 # boost threshold. Default to 0.7
maxlength::Integer # max length of common prefix. Default to 4
end
function Winkler(dist::StringDistance; p = 0.1, threshold = 0.7, maxlength = 4)
p * maxlength <= 1 || throw("scaling factor times maxlength of common prefix must be lower than one")
Winkler(dist, 0.1, 0.7, 4)
end
function compare(s1::AbstractString, s2::AbstractString, dist::Winkler; min_score = 0.0)
# cannot do min_score because of boosting threshold
score = compare(s1, s2, dist.dist)
if score >= dist.threshold
l = common_prefix(s1, s2)[1]
score += min(l, dist.maxlength) * dist.p * (1 - score)
end
return score
end
"""
Partial(dist::StringDistance)
Creates the `Partial{dist}` distance
`Partial{dist}` modifies the string distance `dist` to return the
maximal similarity score between the shorter string and substrings of the longer string
### Examples
```julia-repl
julia> s1 = "New York Mets vs Atlanta Braves"
julia> s2 = "Atlanta Braves vs New York Mets"
julia> compare(s1, s2, Partial(RatcliffObershelp()))
0.4516129032258065
```
"""
struct Partial{S <: StringDistance} <: StringDistance
dist::S
end
function compare(s1::AbstractString, s2::AbstractString, dist::Partial; min_score = 0.0)
s1, s2 = reorder(s1, s2)
len1, len2 = length(s1), length(s2)
len1 == len2 && return compare(s1, s2, dist.dist; min_score = min_score)
len1 == 0 && return 1.0
out = 0.0
for x in qgram(s2, len1)
curr = compare(s1, x, dist.dist; min_score = min_score)
out = max(out, curr)
min_score = max(out, min_score)
end
return out
end
function compare(s1::AbstractString, s2::AbstractString, dist::Partial{RatcliffObershelp}; min_score = 0.0)
s1, s2 = reorder(s1, s2)
len1, len2 = length(s1), length(s2)
len1 == len2 && return compare(s1, s2, dist.dist)
out = 0.0
for r in matching_blocks(s1, s2)
# Make sure the substring of s2 has length len1
s2_start = r[2] - r[1] + 1
s2_end = s2_start + len1 - 1
if s2_start <= 0
s2_end += 1 - s2_start
s2_start += 1 - s2_start
elseif s2_end > len2
s2_start += len2 - s2_end
s2_end += len2 - s2_end
end
i2_start = nextind(s2, 0, s2_start)
i2_end = nextind(s2, 0, s2_end)
curr = compare(s1, SubString(s2, i2_start, i2_end), RatcliffObershelp())
out = max(out, curr)
end
return out
end
"""
TokenSort(dist::StringDistance)
Creates the `TokenSort{dist}` distance
`TokenSort{dist}` modifies the string distance `dist` to adjust for differences
in word orders by reording words alphabetically.
### Examples
```julia-repl
julia> s1 = "New York Mets vs Atlanta Braves"
julia> s1 = "New York Mets vs Atlanta Braves"
julia> s2 = "Atlanta Braves vs New York Mets"
julia> compare(s1, s2, TokenSort(RatcliffObershelp()))
1.0
```
"""
struct TokenSort{T <: StringDistance} <: StringDistance
dist::T
end
# http://chairnerd.seatgeek.com/fuzzywuzzy-fuzzy-string-matching-in-python/
function compare(s1::AbstractString, s2::AbstractString, dist::TokenSort; min_score = 0.0)
s1 = join(sort!(split(s1)), " ")
s2 = join(sort!(split(s2)), " ")
compare(s1, s2, dist.dist; min_score = min_score)
end
"""
TokenSet(dist::StringDistance)
Creates the `TokenSet{dist}` distance
`TokenSet{dist}` modifies the string distance `dist` to adjust for differences
in word orders and word numbers, by comparing the intersection of two strings with each string.
### Examples
```julia-repl
julia> s1 = "New York Mets vs Atlanta"
julia> s2 = "Atlanta Braves vs New York Mets"
julia> compare(s1, s2, TokenSet(RatcliffObershelp()))
1.0
```
"""
struct TokenSet{T <: StringDistance} <: StringDistance
dist::T
end
# http://chairnerd.seatgeek.com/fuzzywuzzy-fuzzy-string-matching-in-python/
function compare(s1::AbstractString, s2::AbstractString, dist::TokenSet; min_score = 0.0)
v1 = unique!(sort!(split(s1)))
v2 = unique!(sort!(split(s2)))
v0 = intersect(v1, v2)
s0 = join(v0, " ")
s1 = join(v1, " ")
s2 = join(v2, " ")
isempty(s0) && return compare(s1, s2, dist.dist; min_score = min_score)
dist0 = compare(s0, s1, dist.dist; min_score = min_score)
min_score = max(min_score, dist0)
dist1 = compare(s0, s2, dist.dist; min_score = min_score)
min_score = max(min_score, dist1)
dist2 = compare(s0, s2, dist.dist; min_score = min_score)
max(dist0, dist1, dist2)
end
"""
TokenMax(dist::StringDistance)
Creates the `TokenMax{dist}` distance
`TokenMax{dist}` combines similarity scores of the base distance `dist`,
its [`Partial`](@ref) modifier, its [`TokenSort`](@ref) modifier, and its
[`TokenSet`](@ref) modifier, with penalty terms depending on string lengths.
### Examples
```julia-repl
julia> s1 = "New York Mets vs Atlanta"
julia> s2 = "Atlanta Braves vs New York Mets"
julia> compare(s1, s2, TokenMax(RatcliffObershelp()))
0.95
```
"""
struct TokenMax{S <: StringDistance} <: StringDistance
dist::S
end
function compare(s1::AbstractString, s2::AbstractString, dist::TokenMax; min_score = 0.0)
s1, s2 = reorder(s1, s2)
len1, len2 = length(s1), length(s2)
dist0 = compare(s1, s2, dist.dist; min_score = min_score)
min_score = max(min_score, dist0)
unbase_scale = 0.95
# if one string is much shorter than the other, use partial
if length(s2) >= 1.5 * length(s1)
partial_scale = length(s2) > (8 * length(s1)) ? 0.6 : 0.9
dist1 = partial_scale * compare(s1, s2, Partial(dist.dist);
min_score = min_score / partial_scale)
min_score = max(min_score, dist1)
dist2 = unbase_scale * partial_scale *
compare(s1, s2, TokenSort(Partial(dist.dist));
min_score = min_score / (unbase_scale * partial_scale))
min_score = max(min_score, dist2)
dist3 = unbase_scale * partial_scale *
compare(s1, s2, TokenSet(Partial(dist.dist));
min_score = min_score / (unbase_scale * partial_scale))
return max(dist0, dist1, dist2, dist3)
else
dist1 = unbase_scale *
compare(s1, s2, TokenSort(dist.dist);
min_score = min_score / unbase_scale)
min_score = max(min_score, dist1)
dist2 = unbase_scale *
compare(s1, s2, TokenSet(dist.dist);
min_score = min_score / unbase_scale)
return max(dist0, dist1, dist2)
end
end