The EXP function returns the natural exponential function of Expression.

## Examples

### Example 1

Plot a Gaussian distribution with a 1/e width of 10 and a center of 50 by entering:

`myPlot = PLOT(EXP(-(FINDGEN(100)/10. - 5.0)^2))`

### Example 2

Create a simple PLOT of the decay of radioactive tritium (H3) in a waste tank, beginning in 1995 and going for 35 years, given the following:

• initial concentration (N0) = 7,000,000 pCi/L
• tank was sealed after initial filling
• half life tritium (t1/2) = 12.32 years
• decay constant tritium (k) = (-ln(2)/t1/2)
• t = number of years from 1995
• concentration in a given year (N) = N0e-kt

Copy and paste the following code at the IDL command line to generate the plot below:

`; Decay constant of tritium.`
`decay=(-(ALOG(2))/12.32) `
` `
`; Initial concentration in the tank in pCi/L.`
`ipCi=7000000`
` `
`; Create the plot using 1995 as the base year.`
`myPlot = PLOT((1995+FINDGEN(35)), (ipCi*EXP(decay*FINDGEN(35))), \$`
`   DIMENSIONS=[753, 500], XTITLE="Year", \$`
`   TITLE="Simple Tritium Decay at Source (pCi/L)", \$`
`   YTITLE="Tritium Concentration (pCi/L)" )`
` `

IDL creates the following plot: ## Syntax

Result = EXP(Expression)

## Return Value

Returns the natural exponential function of the given Expression.

## Arguments

### Expression

The expression to be evaluated. If Expression is double-precision floating or complex, the result is of the same type. All other types are converted to single-precision floating-point and yield floating-point results. The definition of the exponential function for complex arguments is:

EXP(x) = COMPLEX(eRcos I, eRsin I)

where:

R = real part of x, and I = imaginary part of x. If Expression is an array, the result has the same structure, with each element containing the result for the corresponding element of Expression.