vamsi426
Posts: 15
Joined: Mon Apr 04, 2022 1:25 pm

can Bellcurve y-axis values go beyond 1 ?

Hi Team,

I have plotted histogram and bellcurve charts with a data set and I got bell curve y-axis values beyond 1(refer below fiddle).
https://jsfiddle.net/ry01o3qt/

I have plotted the same charts in an excel with same data and I got bell curve y-axis values less than 1. (refer attached image)

1.Can you please confirm which is valid ?
2. can bell curve y-axis values go beyond 1 ?
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kamil.m
Posts: 892
Joined: Thu May 19, 2022 1:33 pm

Re: can Bellcurve y-axis values go beyond 1 ?

Hi there,

Please do not duplicate posts on the forum. I have deleted the second topic, so let's continue the discussion here.

This is more of a maths question rather than a Highcharts one. I have no idea how the bell curve is calculated in Excel, but in Highcharts, we use the equation from Wikipedia.
https://en.wikipedia.org/wiki/Normal_distribution

And once you calculate it yourself, you will see why the bell curve values exceed 1. If you have a standard deviation below 1, you get such values on the yAxis. But when it comes to a bell curve, the shape is the most important factor, not the yAxis values.

If you take the f(x) equation and divide the 1 by σ√2π - just like it says in the Wikipedia equation, you get the y values. And if you use a standard deviation σ like i.e 0.1 the equation will always return more than one, since 1 divided by value below 1 = y value >1.

I hope that it's clear to you now,
Best regards!
Kamil Musiałowski
Highcharts Developer

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