(PECL stats >= 1.0.0)

stats_cdf_exponentialCalculates any one parameter of the exponential distribution given values for the others


stats_cdf_exponential(float $par1, float $par2, int $which): float

Returns the cumulative distribution function, its inverse, or one of its parameters, of the exponential distribution. The kind of the return value and parameters (par1 and par2) are determined by which.

The following table lists the return value and parameters by which. CDF, x, and lambda denotes cumulative distribution function, the value of the random variable, and the rate parameter of the exponential distribution, respectively.

Return value and parameters
which Return value par1 par2
1 CDF x lambda
2 x CDF lambda
3 lambda x CDF



The first parameter


The second parameter


The flag to determine what to be calculated


Returns CDF, x, or lambda, determined by which.

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