I dislike education acronyms, but I can make exceptions for mathematical ones.  One of my favourite topics in A-level Maths is full to bursting with them: DRVs, CRVs, PDF, CDF.  This is a visual representation of the CDF (cumulative distribution function) of a CRV (continuous random variable), which is the function for the area under the curve from x=-∞ to any other value, a, or more specifically, P(X<a).  Take note of the syntax for piecewise functions.

The PDF (probability density function) of the CRV I’ve used* is

pdf

and its CDF is

cdf.

But you don’t need to know the CDF to represent it in Desmos, you just need to use inequalities to shade the region between the x-axis and the curve, with a slider for the variable value of x.  The syntax is a little unusual, but take a look and you’ll see how it’s done.  The same principle was used in my model for normal distribution.

 

*It’s taken from the Edexcel S2 exam, June 2012, question 7.

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