Plotting the results of a For Loop in R

Question

I'm trying to plot the results of a For Loop, as follows:

marketPrice = 100
strikePrice = 125

tau = 1

dividendYield = .03
interestRate = .02

sigma = .25

lowerMarketBound = 100
upperMarketBound = 150

stepIncrement = 5

callPrice = NULL
putPrice = NULL

plot(marketPrice, callPrice)

for (marketPrice in seq(from=lowerMarketBound, to=upperMarketBound,
 by=stepIncrement)){

d1 = ((log(marketPrice / strikePrice)) + ((interestRate + 
    (sigma**2/2)) * f_tau)) / (sigma * sqrt(tau))
d2 = d1 - (sigma * sqrt(tau))

print(marketPrice)

callPrice = marketPrice * pnorm(d1) - pnorm(d2) * strikePrice * 
    exp(1)^(-interestRate * tau)
putPrice = strikePrice * exp(1)^(-interestRate * tau) * pnorm(-d2) -     
    marketPrice * pnorm(-d1)

print (callPrice)
print (putPrice)
plot(marketPrice, callPrice)
}

The last line of the code calls plot(). I was expecting to see a plot of the marketPrice variable vs. the callPrice variable. Instead, I'm seeing a plot of only the LAST marketPrice and callPrice of the loop (in this case, 150 and 31.46, respectively).

Is there a way to plot all of the results of a For Loop?

Answer 1

You could store the values in a matrix during the loop and plot the whole series at the end.

tau = 1

dividendYield = .03
interestRate = .02

sigma = .25

lowerMarketBound = 100
upperMarketBound = 150
stepIncrement = 5
marketPrice = seq(from=lowerMarketBound, to=upperMarketBound,
                  by=stepIncrement)
strikePrice = 125



callPrice = rep(0,length(marketPrice))
putPrice = NULL

for (i in 1:length(marketPrice)){

  d1 = ((log(marketPrice[i] / strikePrice) + (interestRate + (sigma**2/2)) * tau) / (sigma * sqrt(tau)))
  d2 = d1 - (sigma * sqrt(tau))

  print(marketPrice[i])

  callPrice[i] = marketPrice[i] * pnorm(d1) - pnorm(d2) * strikePrice * exp(1)^(-interestRate * tau)
  putPrice = strikePrice * exp(1)^(-interestRate * tau) * pnorm(-d2) - marketPrice[i] * pnorm(-d1)

  print (callPrice[i])
  print (putPrice)
}

plot(marketPrice, callPrice)