Out of memory- infinite recursion error

Hi, my code below keeps on coming up with an infinite recursion error, could someone tell me how to fix this please?

[Cicely Blocksidge]

sorry, the code is attactched in the screenshot and here

[Jeff Miller]

Not sure what you are trying to compute so I can't say how to "fix" it, but to avoid an infinite recursion there have to be some circumstances under which your function does not call itself, e.g., as checked with an 'if' statement or some such.

[Jan]

@Cicely Blocksidge: Please post code as text and not as screenshot. Then the readers can suggest an improvement without having to retype your complete code.

[Cicely Blocksidge]

Code is here, thanks for the suggestion. It's a code to plot a figure of x against the mathematical function y. there was also a mistake in the original code yes as i was not calling upon i- have changed that now. It no longer comes up with the infinite recursion error, but instead creates over 100 new figures, and takes a while to run? Any advice on how to fix this would be greatly appreciated. Ideally, the code is meant to produce an upside down parabola.

% code to plot a graph of x against y

function[y] = cicelyscode(x)

D=10^-7;

v=10^-5;

t=1;

figure

for i= 1:length(x)

y= (1/sqrt(4*pi*D*t)) * exp(-((i-v*t).^2)/4*D);

x= [0:0.01:2];

y= cicelyscode(x)

plot(x,y)

end

end

Answer 1

[Jan]

Posting a failing code only does not allow to fix it, because the readers do not have a chance to guess the intention of the code reliably. Therefore you have to explain the purpose either in the text or better in exhaustive comments inside the code.

You have created a loop over the counter i, but i is not used anywhere in the body of the loop.

Calling a function recursively from inside the function without any limitation is an "infinite recursion". This cannot work.

Maybe all you need is

function y = cicelysode(x)
D = 1e-7;  % More efficient than the expensive 10^-7
v = 1e-5;
t = 1;
y = exp(-0.25 * D * (x - v * t) .^ 2) / sqrt(4 * pi * D * t);
end

[Cicely Blocksidge]

ps thanks for pointing out i did not use i in the loop- that was a mistake!

Code is here, thanks for the suggestion. It's a code to plot a figure of x against the mathematical function y. there was also a mistake in the original code yes as i was not calling upon i- have changed that now. It no longer comes up with the infinite recursion error, but instead creates over 100 new figures, and takes a while to run? Any advice on how to fix this would be greatly appreciated. Ideally, the code is meant to produce an upside down parabola.

% code to plot a graph of x against y

function[y] = cicelyscode(x)
D=10^-7;
v=10^-5;
t=1;
 
figure
for i= 1:length(x)
    y= (1/sqrt(4*pi*D*t)) * exp(-((i-v*t).^2)/4*D);
    x= [0:0.01:2];
    y= cicelyscode(x)
    plot(x,y)
end

[Jan]

The code still contains a line, which falls itself recursively. But why?

How do you call it? If I remove the recursive call, I get a diagram:

function cicelyscode
D = 10^-7;
v = 10^-5;
t = 1;
x = 0:0.1:2;
figure
axes('NextPlot', 'add');   % Equivalent to: hold on
for i = 1:length(x)
    y = (1 / sqrt(4*pi*D*t)) * exp(-((x(i) - v * t) .^ 2) / 4*D);
    plot(x(i), y, '.');
end
end

This would work without a loop also:

function cicelyscode
D = 10^-7;
v = 10^-5;
t = 1;
x = 0:0.1:2;
y = (1 ./ sqrt(4*pi*D*t)) * exp(-((x - v * t) .^ 2) / 4 * D);
plot(x, y);
end

Answer 2

[Steven Lord]

Let's say I call cicelyscode with an input argument.

cicelyscode([0 1])

This will create a figure then start the for loop to iterate over the elements of x. You use that value of i (but do not use x at all) to compute y, then overwrite the x variable [0 1] that I passed into cicelyscode and then calls

cicelyscode(0:0.01:2)

This will create a figure then start the for loop to iterate over the elements of x. You use that value of i (but do not use x at all) to compute y, then overwrite the x variable 0:0.01:2 that I passed into cicelyscode and then calls

cicelyscode(0:0.01:2)

This will create a figure then start the for loop to iterate over the elements of x. You use that value of i (but do not use x at all) to compute y, then overwrite the x variable 0:0.01:2 that I passed into cicelyscode and then calls

cicelyscode(0:0.01:2)

This will create a figure then start the for loop to iterate over the elements of x. You use that value of i (but do not use x at all) to compute y, then overwrite the x variable 0:0.01:2 that I passed into cicelyscode and then calls

cicelyscode(0:0.01:2)

etc.

I could repeat this copy and paste a few more times, but I think you get the picture that MATLAB will never reach to the plot call in your function.

So some of the issues are:

1) You never use the x input argument with which the user calls the function

2) Then you overwrite that unused input argument with a different vector.

3) Every call to your function results in a new figure being opened and a new call to cicelyscode.

So you've showed us how you've tried to solve the problem with which you've been presented, but you haven't told us anything about the problem itself. I suspect that you don't need recursion at all, but you could confirm or reject my suspicion by showing us the problem statement. It's entirely possible this could be a four line script:

% Step 1: Define x
% Step 2: Use x to compute y
% Step 3: Open the figure window. This is optional since step 4 will do it if necessary
% Step 4: Call plot

If you need a function instead of a script, step 1 could be replaced with defining a function that accepts x as input.