Values on line chart as % of first value

[greendot]

Hi,

I'm working on an analysis of a used car value depreciation (value loss) over time. I have a large database of offers with price and car age. I've created a sheet containing filters (e.g. car brand and model) and a line chart with car age plotted on the X axis and the average car price plotted on the Y axis.

This gives me a curve showing how a used car value typically deteriorates over time. Yet, the data points are in absolute terms and I would like to present the depreciation in percentage terms (the way it's usually done). Meaning, value for a new car would be presented as 100%, for a 1-year-old car as e.g. 85%, 2-year-old car as 60%, etc. (i.e. average used car prices would be presented as a % of an average new car price). 

Is there a way to do it using calculated fields/dimensions or in any other quick way (preferably without altering the data)?

Any guidance would be much appreciated. 

[MohammedMustaq]

Hi,

Can you provide some sample data.

Thanks
Mustaq

[vikramv]

I guess, you need to use an expression that would be like (1-(x/100))*100  . Where x is your actual measure usage % in decimals.

[greendot]

Here is how the chart look like right now:

As you can see, each line represents the average price of a used car of a certain age (1-5) in years 2012, 2015 and 2018. I would like to show the value loss in percentage terms for each year, meaning that all three lines would start at the same point (100%) and then the depreciation of the average price (change of price for the same model but older) would be shown. This way I could easily see if there was an actual shift in the depreciation curve or is it just inflation of new car prices. 

I guess the question comes down to how can you refer to the first value of the time series in a calculated field.