Fetch specific record value from a table in PowerBI - powerbi

Question

I'm trying to dynamically calculate the % Change of the prices in a table, where each price will be compared with the first price (Price in the first record, ordered by date). There is a date filter, so the first record being displayed will change accordingly. Date column values are unique.
Assume the user applies a filter for date BETWEEN '15-APR-2021' AND '30-APR-2021'. Then the expected '% Change' column would look like:
For this example, I had to hardcode the starting price in the calculation:
% Change = (('table1'[price]/3218.95) -1)*100
I tried the below, but it doesn't return a static value of 3218.95. Instead, it re-calculates it at record level rather filtered table level as we see in the above screenshot :
first_date = (MIN(table1[Date]))
first_price = LOOKUPVALUE('table1'[price],table1[Date],'table1'[first_date])
% Change = (('table1'[price]/first_price) -1)*100
I'm new to PowerBI DAX. Logically the SQL would look like so:
SELECT
date,
price,
((
price /
( -- Gets the first price
SELECT price FROM table1
WHERE date IN (SELECT MIN(date) FROM table1 WHERE date BETWEEN '15-APR-2021' AND '30-APR-2021')
)
)-1) * 100 as '% change'
FROM table1
WHERE date BETWEEN '15-APR-2021' AND '30-APR-2021'

Answer 1

IF you want to get the first price you can use the following DAX:
first_price = CALCULATE(MIN('table1'[price]), FILTER( 'table1', MIN(table1[Date])))
As for the % Change:
% Change =
var curPrice = 'table1'[price]
var first_price = CALCULATE(MIN('table1'[price]), FILTER( 'table1', MIN(table1[Date])))
return ((curPrice/first_price) - 1) * 100