Error: Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.

Hi all, Im working on a code that simulates a stock price over two years and then compares it to a strike price (call options). I want to simulate the stock price 3000 for each starting value (30 to 150), then take the average payout (for that particular staring price) and plot that vs the starting price. The idea is that if the final price is higher than the strike price (starting price) you get a payout equal to the difference between the final and strike price, if not you get 0.

I keep getting an error (Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.) gives the error in the line

for S(1, :) = 30 : 150

Here is my code

r = 0.05;
T = 2;
dt = 1/365;
sigma = sqrt(r);
rng('shuffle')
eta = randn(1, 365*T+1);
n_iterations = 3000;
S = zeros(365*T, n_iterations);
 
for S(1, :) = 30 : 150
    n = 1 : n_iterations;
    for k = 1 : 365*T
    S(k+1, n) = S(k, n) + S(k, n).*r.*dt + sqrt(dt).*sigma.*S(k, n).*eta(k, n);
    end
    
    strike = S(1, :);
    price = S((365*T + 1), :);
    
    eurocallreturn(strike, price);
    
    avereturn = mean(eurocallreturn);
    
    hold on
    plot(strike, avereturn)
    xlabel('Price')
    ylabel('Return')
end
 
function R = eurocallreturn(strike, price)
if price > strike
    R = price - strike;
    
else if price <= strike
        R = 0;
    end
end
    
end

Answer 1

[Walter Roberson]

In MATLAB, the variable immediately after the keyword for must be a simple variable, not indexed in any way -- no () indexing, no {} indexing, no dot indexing. For example it is not permitted to write

for counters.laps = 1 : 20

You will need to rewrite to something like

    for Sidx = 30 : 150
        S(1, :) = Sidx;
        ....
    end

[Dawid Brits]

I think that did the trick, however its giving me a different error

Index in position 2 exceeds array bounds (must not exceed 731).

Error in assig5part2b (line 16)

S(k+1, n) = S(k, n) + S(k, n).*r.*dt + sqrt(dt).*sigma.*S(k, n).*eta(k, n);

is this because I'm initializing the vector in the wrong size?

Thanks in advance

[Walter Roberson]

It is a problem with you you initialize and use eta which I answered in your other Question.

Answer 2

[Manoj Shukla]

Hello,

Please help me.

Email Id:- [e-mail]

0.3764
    0.5673
    0.1168
    0.1535
    0.6345

Train Accuracy: 83.050847
Expected accuracy (with lambda = 1): 83.1 (approx)
>> 
>> 
>> submit()
'parts' requires one of the following:
  Automated Driving Toolbox
  Navigation Toolbox
  Robotics System Toolbox
  Sensor Fusion and Tracking Toolbox

Error in submitWithConfiguration (line 4)
  parts = parts(conf);

Error in submit (line 40)
  submitWithConfiguration(conf);

Thanks & Regards,

Manoj

[Walter Roberson]

submitWithConfiguration contains code in which the name parts is used both for a function and as a variable name. With recent changes to MATLAB, MATLAB cannot locate the function. The repair for this is to change submitWithConfiguration to use a different variable name instead of parts .

Answer 3

[Merve Özkanat]

Hi, I get the same error. Could you help me?

global a b t E nu

GP1=(-a/sqrt(3),-b/sqrt(3));
GP2=(a/sqrt(3),-b/sqrt(3));
GP3=(a/sqrt(3),b/sqrt(3));
GP4=(-a/sqrt(3),b/sqrt(3));