straddle: Straddle Spread
In FinancialMath: Financial Mathematics for Actuaries

Gives a table and graphical representation of the payoff and profit of a long or short straddle for a range of future stock prices.

1	straddle(S,K,r,t,price1,price2,position,plot=FALSE)

`S`	spot price at time 0
`K`	strike price of the call and put
`r`	continuously compounded yearly risk free rate
`t`	time of expiration (in years)
`price1`	price of the long call with strike price K
`price2`	price of the long put with strike price K
`position`	either buyer or seller of option ("long" or "short")
`plot`	tells whether or not to plot the payoff and profit

Stock price at time t =S_t

Long Position:

For S_t<=K: payoff =K-S_t

For S_t>K: payoff =S_t-K

profit = payoff - (price1 + price2)*e^{r*t}

Short Position:

For S_t<=K: payoff =S_t-K

For S_t>K: payoff =K-S_t

profit = payoff + (price1 + price2)*e^{r*t}

A list of two components.

`Payoff`	A data frame of different payoffs and profits for given stock prices.
`Premiums`	A matrix of the premiums for the call and put options, and the net cost.