MATLAB keeps returning that the statement is not inside any function, and has a parse error, even though both are clearly defined already. How do I fix this?

Matlab keeps returning to me that the statement is not inside any function, and when I run/print the function that was clearly defined above, it says that there is a parse error (in this case, the main() function that was called), and that the function main() might be unused (which is wrong because I definitely called it under the end of the function). Or is this a problem BECAUSE I ran the code after the function end? But I've already tried otherwise as well and it still doesn't work. Please help!!

% define the run simulation function

function run_simulation()

% define the time vector

t = linspace(0,5*365,100);

% call rate of change of costs of operation function

rate_of_change_costs_of_operation(t);

end

% Define the sales rate function

function sales_rate = sales(t)

if t < 365*2 % sales rate for first two years

sales_rate = 5;

else % sales rate for all subsequent years

sales_rate = 7;

end

end

% Define the operation costs function

function operation_costs = costs(t)

% Define the parameters

daily_operation_cost = 1000;

% Calculate the operation costs at time t

operation_costs = cumsum(daily_operation_cost)*t;

end

% Define the rate of change of costs of operation function

function rate_of_change_costs_of_operation(t)

% Calculate the total number of sales using numerical integration

daily_customer_arrival_rate = 10;

daily_sales_rate = sales(t);

total_sales = trapz(t, daily_customer_arrival_rate .* sales(t) .* daily_sales_rate);

% Calculate the total costs of operation using numerical integration

total_costs = trapz(t, costs(t));

% Calculate the rate of change of sales using partial differential equations

% Define the PDE system

dSdt = @(t,S) daily_customer_arrival_rate .* total_sales - S .* daily_sales_rate;

dSdt_bc = @(Sleft,Sright) [Sleft; Sright];

% Solve the PDE system

x = linspace(0,5*365,100); % spatial mesh

sol = pdepe(0,dSdt,dSdt_bc,zeros(size(x)),x,t); % solve PDE system

% Extract the solution and calculate the rate of change of sales

S = sol(:,:,1);

dSdt_num = gradient(S(:,1), x(2)-x(1)); % numerical derivative

% Calculate the rate of change of operation costs using partial differential equations

% Define the PDE system

dCdt = @(t,C) daily_operation_cost - C .* interp1(x, gradient(S(:,1), x(2)-x(1)), t);

dCdt_bc = @(Cleft,Cright) [Cleft; Cright];

% Solve the PDE system

x = linspace(0,5*365,100); % spatial mesh

C0 = zeros(size(x)); % initial condition

sol = pdepe(0,dCdt,dCdt_bc,C0,x,t); % solve PDE system

% Extract the solution and plot the results

C = sol(:,:,1);

plot(x,C);

xlabel('Time (days)');

ylabel('Costs of Operation');

title('Rate of Change of Costs of Operation');

end % end of rate_of_change_costs_of_operation function

function main()

run_simulation();

end

main();

this is the error that returned to me:

>> rate_of_change_of_costs_of_operation

Error: File: rate_of_change_of_costs_of_operation.m Line: 74 Column: 1

This statement is not inside any function.

(It follows the END that terminates the definition of the function "main".)

Answer 1

[Cris LaPierre]

In a MATLB script, all functions must be defined at the bottom (or below) the script code (see here).

Move main() to the first line of your script.