Irish Soda Bread Lab123 recipes

Irish Soda Bread Lab

Two styles in 123 Irish soda bread recipes

Leave the recipe names aside and group the 123 recipes by their 6 ingredient ratios alone, so that recipes built alike land together. Each group is named only by the numbers: the ingredients where its recipes sit furthest from the middle of all 123.

The data splits best into two groups, and they separate: a silhouette of 0.27, on a scale where 0 is no separation and 1 is complete. They still touch at the edges, so a recipe near a boundary could sit in either.

The recipes on one map

Every recipe, placed on the two directions along which the ratios vary most (a principal component projection). Close dots are recipes built alike. The lettered rings mark the middle of each group.

AB
Across →
More butter, egg and sugar to the right; 33% of the variation.
Up ↑
More baking soda and salt upward; 22% of the variation.

Along the first direction butter, egg and sugar all rise together, each measured against the flour. A recipe sits far along it by using more of them or by using less flour, which the ratios cannot tell apart. The groups sit apart mostly along this direction.

The two groups

ALess butter and egg

77 recipes · 63% of all 123 · median oven 400°F (205°C), 35 min

Where it differs from all recipes

  • Buttermedian 0% vs 5.6% for all

    average rank: 34th percentile of all recipes · none in 58% (all recipes 38%)

  • Eggmedian 0% vs 0% for all

    average rank: 34th percentile of all recipes · none in 85% (all recipes 55%)

  • Sugarmedian 0% vs 1% for all

    average rank: 37th percentile of all recipes · none in 62% (all recipes 45%)

Its median recipe, at 500 g flour

Median recipe of group A in grams, against the median of all recipes
IngredientGroup AAll
Buttermilk415 g420 g
Baking soda7 g6 g
Butternone28 g
Sugarnone5 g
Eggnonenone
Salt6 g6 g

Each line is the group's median for that ingredient, scaled to 500 g of flour.

Closest to the middle of the group

BWith butter, with egg

46 recipes · 37% of all 123 · median oven 375°F (190°C), 48 min

Where it differs from all recipes

  • Buttermedian 15% vs 5.6% for all

    average rank: 77th percentile of all recipes · none in 4% (all recipes 38%)

  • Eggmedian 10% vs 0% for all

    average rank: 76th percentile of all recipes · none in 4% (all recipes 55%)

  • Sugarmedian 10% vs 1% for all

    average rank: 71st percentile of all recipes · none in 17% (all recipes 45%)

Its median recipe, at 500 g flour

Median recipe of group B in grams, against the median of all recipes
IngredientGroup BAll
Buttermilk425 g420 g
Baking soda6 g6 g
Butter75 g28 g
Sugar50 g5 g
Egg50 gnone
Salt6 g6 g

Each line is the group's median for that ingredient, scaled to 500 g of flour.

Closest to the middle of the group

How the groups are found

Each ratio is converted to a z-score (how many standard deviations a recipe sits from the mean), capped at 3 so one extreme recipe cannot claim a group, and k-means sorts the recipes into k groups, trying k from 2 to 4. Each k runs from 16 fixed starting points and keeps the tightest result, so the page is the same on every build. No group may hold fewer than 13 recipes.

The number of groups is the one with the best silhouette, which compares how close each recipe is to its own group with how close it is to the next one. By number of groups: 2 groups 0.27 · 3 groups 0.20 · 4 groups 0.17. At 0.25 or more the page calls the groups separate; from 0.18 to 0.25, overlapping; under 0.18, no clear styles.

A group's name lists the one to three ingredients where its recipes rank furthest from the middle of all 123, on average. “More” and “less” are relative to the whole dataset, and the names say nothing about texture or taste, which the ratios alone do not show. The median recipe of a group is, like the typical recipe on the overview, the middle of each ingredient separately, not one real recipe. The recipes listed under each group are the ones nearest its center, at most two from any one site.