Allow comparing products by cost per mass/volume of nutrients

[aleksejrs]

What

1. Enter prices (and quantities, if applicable) of two or more products/categories
2. Get a table comparing the costs of each nutrient per gram or milliliter (maybe along with the normal quantity comparison if possible).

[TaciteOFF]

Prices are a very touchy topic and I think it shouldn't be directly implemented in Open Food Facts but on a second project. To make our database grow bigger we need to have verified datasets from manufacturers. There's a high chance that manufacturers will never want to help us if we clearly show prices.

See #prices on our Slack for more information.

[aleksejrs]

I mean only entering prices in the comparison UI, not storing them.

[aleksejrs]

Teolemon also mentioned "how many calories per dollar?"

[aleksejrs]

The prices should be easily editable without reloading the page (like in Android's calculator).

[aleksejrs]

An imperfect graphical comparison.

• The widths mean the relative amounts of the products you can purchase with a unit of money. Product A (left) is 3 times cheaper per mass/volume than product B.
• Heights of the small rectangles are the relative amounts of nutrients in a product.
• The areas of the small rectangles reflect (I can't imagine exactly how) the relative amounts of the nutrients you can purchase with a unit of money.

Product A contains less Green nutrient than product B does, but you can get more of it for the same price, if you don't mind the Yellow nutrient and the grey Rest, of which there is more in A than in B.

Red is hard to compare in this case, maybe numbers would help.

P.S.: maybe nutrients with very low quantities could be shown in separate big rectangles.

[aleksejrs]

https://ru.openfoodfacts.org/product/4607177745602 about 14 roubles for 350 g. https://ru.openfoodfacts.org/product/4601347002052 about 28 roubles for 400 g.

First column shows how much of a nutritional value you get for 28 ₽, and the second column shows how much of the correspondent value of the other product that is.

Бородинский, 2 halves, 28 ₽ for 700 g:

• p 47,6 1.50
• f 9,1 0.91
• c 278.6 1.36
• e 5894 1.34

Ароматный, 28 ₽ for 400 g:

• p 31.6 0.66
• f 10 1.09
• c 204.4 0.73
• e 4384 0.74
• sliced (time)
• tasty (subjective)

Things to consider:

• Бородинский lists its carbohydrates as "углеводы усвояемые" (digestible carbohydrates), so those could include fiber while those of ароматный do not, making the difference even bigger?
• Ароматный lists vitamins.
• Ingredients.
• There may be other differences that cannot be found on the label, but may be mentioned in the GOSTs.

[teolemon]

We're now talking of shrinkflation

[teolemon]

@aleksejrs @TaciteOFF @raphael0202 @raphodn https://prices.openfoodfacts.org/app/prices starts solving this.