How do i set the apex (intercept) when scaling

Lets assume this is the d3 code

this.y = d3
	.scalePow()
	.exponent(2)
	.domain([2000, 10000])
	.range([600, 0]);

What it does is mapping 2000 to 600, 10000 to 0, and everything inbetween is scaled by some quadratic formula which has its apex at 2000. Now the question is easy, how to i set the apex to say 6000? i want detailed values (big gaps) in the 6000 and narrow steps in the outer rim.

I added a picture i drew with my fingers for clarificarion. I might add a better pic later

I am not sure if parabola apex is the right word, in german its called Scheitelpunkt

Simply, change the .exponent(2) to .exponent(1/2):

This has everything to do with the fact that x^2 and sqrt(x) are inverse functions.

What you want can be done using a Symlog scale, which provides a bi-symmetric log transformation.

For that to work, what you call the apex (that is, 6000) will be the zero in the scale, and the domain will be [-4000, 4000] (since 2000 = 6000 - 4000, and 10000 = 6000 + 4000).

Also, don't forget to format the ticks, adding 6000, and obviously the values you pass to the scale as well.

Here's the demo:

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

const svg = d3.select("svg")
  .attr("width", 600);

const scale = d3.scaleSymlog()
  .constant(500)
  .range([20, 580])
  .domain([-4000, 4000]);

const axis = d3.axisBottom(scale).tickFormat(d => d + 6000);

svg.append("g").attr("transform", `translate(0,)`).call(axis)

<!-- language: lang-html -->

<script src="https://d3js.org/d3.v7.min.js"></script>
<svg></svg>

<!-- end snippet -->