Exponential Distribution. The exponential distribution function is defined as:

f(x) = * e-x
0 x < , > 0

where
   (lambda) is an exponential function parameter (an alternative parameterization is scale parameter b=1/)
 e      is the base of the natural logarithm, sometimes called Euler's e (2.71...)

The graphic above shows the shape of the Exponential distribution when lambda equals 1.

Exponential Function. This fits to the data, an exponential function of the form:

y = b*exp(q*x)