Finding lowest value with no overlapping dates - google-sheets

Question

I have a spreadsheet with criteria, a start and end date, and a value. The goal is to find the lowest value for each unique criteria and start date without overlapping dates (exclusive of end date). I made a pivot table to make it easier for myself but I know there is probably a way to highlight all valid rows that meet the above requirements with some formula or conditional formatting.
I have attached a google drive link where the spreadsheet can be found here and I have some images of the sheet as well. I know that it might be possible with conditional formatting but I just don't know how to combine everything I want it to do in a single formula.
Example below:
Row 2 is a valid entry because it has the lowest value for Item 1 starting on 03-15-2021, same with row 9.
Row 5 is valid because the start date does not fall within the date range of row 2 (exclusive of end date)
Row 7 is not valid because the start date is between the start and end date of row 6

Answer 1

You may add a bounded script to your project. Then you can call it either with a picture/drawing that has the function assigned (button-like), or adding a menu to Google Sheets.
From what you said in the question and the comments, this seems to do what you are trying. Notice that this requires the V8 runtime (which should be the default).
function validate() {
// Get the correct sheet
const spreadsheet = SpreadsheetApp.getActiveSpreadsheet()
const sheet = spreadsheet.getSheetByName('Sheet1')
// Get the data
const length = sheet.getLastRow() - 1
const range = sheet.getRange(2, 1, length, 4)
const rows = range.getValues()
const data = Array.from(rows.entries(), ([index, [item, start, end, value]]) => {
/*
* Row Index
* 1 Criteria 1
* 2 Item 1 0
* 3 Item 1 1
* 4 Item 1 2
*
* row = index + 2
*/
return {
row: index + 2,
criteria: item,
start: start.getTime(),
end: end.getTime(),
value: value
}
})
// Sort the data by criteria (asc), start date (asc), value (asc) and end date (asc)
data.sort((a, b) => {
let order = a.criteria.localeCompare(b.criteria)
if (order !== 0) return order
order = a.start - b.start
if (order !== 0) return order
order = a.value - b.value
if (order !== 0) return order
order = a.end - b.end
return order
})
// Iterate elements and extract the valid ones
// Notice that because we sorted them, the first one of each criteria will always be valid
const valid = []
let currentCriteria
let currentValid = []
for (let row of data) {
if (row.criteria !== currentCriteria) {
// First of the criteria
valid.push(...currentValid) // Move the valids from the old criteria to the valid list
currentValid = [row] // The new list of valid rows is only the current one (for now)
currentCriteria = row.criteria // Set the criteria
} else {
const startDateCollision = currentValid.some(valid => {
row.start >= valid.start && row.start < valid.end
})
if (!startDateCollision) {
currentValid.push(row)
}
}
}
valid.push(...currentValid)
// Remove any old marks
sheet.getRange(2, 5, length).setValue('')
// Mark the valid rows
for (let row of valid) {
sheet.getRange(row.row, 5).setValue('Valid')
}
}
Algorithm rundown
We get the sheet that we have the data in. In this case we do it by name (remember to change it if it's not the default Sheet1)
We read the data and transform it in a more an array of objects, which for this case makes it easier to manage
We sort the data. This is similar to the transpose you made but in the code. It also forces a priority order and groups it by criteria
Iterate the rows, keeping only the valid:
We keep a list of all the valid ones (valid) and one for the current criteria only (currentValid) because we only have to check data collisions with the ones in the same criteria.
The first iteration will always enter the if block (because currentCriteria is undefined).
When changing criteria, we dump all the rows in currentValid into valid. We do the same after the loop with the last criteria
When changing criteria, the CurrentValid is an array with the current row as an element because the first row will always be valid (because of sorting)
For the other rows, we check if the starting date is between the starting and ending date of any of the valid rows for that criteria. If it's not, add it to this criteria's valid rows
We remove all the current "Valid" in the validity row and fill it out with the valids
The cornerstone of the algorithm is actually sorting the data. It allows us to not have to search for the best row, as it's always the next one. It also ensures things like that the first row of a criteria is always valid.
Learning resources
Javascript tutorial (W3Schools)
Google App Scripts
Overview of Google Apps Script
Extending Google Sheets
Custom Menus in Google Workspace
Code references
Class SpreadsheetApp
Class Sheet
Sheet.getRange (notice the 3 overloads)
let ... of (MDN)
Spread syntax (...) (MDN)
Arrow function expressions (MDN)
Array.from() (MDN)
Array.prototype.push() (MDN)
Array.prototype.sort() (MDN)
Date.prototype.getTime() (MDN)
String.prototype.localeCompare() (MDN)