Output argument 'fy' is not assigned on some execution paths

function [fz,x1,fy,M,rills] = fcn(u,m,w,v,r)

if u>=0.436

fz=0;

x1=0;

return;

end

fz = 2*(1+0.4*-m)*739130*(0.436-u);

x1=0.436-u;

r0=2*r/3;

rills=(w*r0-v)/max([abs(v) abs(w*r0) 0.1]);

if (0.13<rills)&&(rills<=1)

fy=(0.77-0.32*rills)*fz;

M=(0.77-0.32*rills)*fz*r0;

elseif -0.13<rills&&rills<=0.13

fy=(5.62*rills)*fz;

M=(5.62*rills)*fz*r0;

else

fy=0.5*fz;

M=0.5*fz*r0;

end

Answer 1

[Voss]

This function returns without assigning a value to fy (and M and rills) whenever u >= 0.436.

if u>=0.436
    fz=0;
    x1=0;
    return; % returns here. at this point fy, M and rills are unassigned
end

[Voss]

Perhaps you meant to do this?

function [fz,x1,fy,M,rills] = fcn(u,m,w,v,r)
if u>=0.436
    fz=0;
    x1=0;
else
    fz = 2*(1+0.4*-m)*739130*(0.436-u);
    x1=0.436-u;
end
r0=2*r/3;
rills=(w*r0-v)/max([abs(v) abs(w*r0) 0.1]);
if (0.13<rills)&&(rills<=1)
   fy=(0.77-0.32*rills)*fz;
    M=(0.77-0.32*rills)*fz*r0;
elseif -0.13<rills&&rills<=0.13
    fy=(5.62*rills)*fz;
    M=(5.62*rills)*fz*r0;
else
    fy=0.5*fz;
    M=0.5*fz*r0;
end

[翰旭]

thank for you help! it is successful

[Voss]

You're welcome! If you have any questions, let me know.

[翰旭]

"returns here. at this point fy, M and rills are unassigned",fz=0,so,fy,M should be zero;so why fy, M, rills are unassigned?

[Voss]

"fz=0,so,fy,M should be zero"

fy and M are whatever you assign them to be. If you don't assign them, they are unassigned. If the function returns with them unassigned, you get the error you saw.

The code in my comment effectively sets them to zero when fz is zero, because instead of returning early, the code continues to the calculation of fy and M, which will both be zero when fz is zero.

Answer 2

[Manan Jain]

Hi!

The warning message "Output argument 'fy' is not assigned on some execution paths" means that there are scenarios in the function where the variable fy might not be assigned a value. In MATLAB, all output variables in a function must be assigned a value before the function returns. If there are paths in the code where fy might not be assigned, it could lead to unexpected behavior when the function is called.

The warning occurs in the case where the condition (0.13 < rills) && (rills <= 1) and the condition (-0.13 < rills) && (rills <= 0.13) are both false. In this case, the fy variable won't be assigned a value, and it can lead to an issue when the function is called with the expectation that fy will always be an output.

To fix this warning, you should make sure that fy is assigned a value in all possible execution paths.

I hope this helps!

Thanks

[翰旭]

If the condition (0.13 < rills) && (rills <= 1) and the condition (-0.13 < rills) && (rills <= 0.13) are both false,why the code does not execute the third condition"else".

[Dyuman Joshi]

What makes you think the code is not executing the 3rd condition?

The if-else conditions are not the problem in your code.

If you want a solution, you will have to provide the information I have asked above in the comment.

rills=2;

if (0.13<rills)&&(rills<=1)
   disp('if')
   %fy=(0.77-0.32*rills)*fz;
    %M=(0.77-0.32*rills)*fz*r0;
elseif -0.13<rills&&rills<=0.13
    disp('elseif')
    %fy=(5.62*rills)*fz;
    %M=(5.62*rills)*fz*r0;
else
    disp('else')
    %fy=0.5*fz;
    %M=0.5*fz*r0;
 end

else

[翰旭]

this image can you know the information

[Image Analyst]

Try stepping through the code and looking at the variables. In other words use debugging like everyone else does.

Debugging in MATLAB | Doug's MATLAB Video Tutorials

Answer 3

[Image Analyst]

If you're not going to assign the outputs in all scenarios, you can initialize the variables to null. Actually I do this by habit for all my functions just as a good habit:

function [fz, x1, fy, M, rills] = fcn(u, m, w, v, r)
% Initialize outputs to null.
fz = [];
x1 = [];
fy = [];
M = [];
rills = [];
% Then the rest of the code.

that way at least the variables will have some value, even though it's null, and you will avoid the error. Later if you get null returned in your main calling program and were not expecting that you can step through it with the debugger and figure out what if blocks you did and did not go into and figure out why some variable never got assigned to something other than null.

Of course you don't have to initialize them to null. You can assign them whatever values you want.

[翰旭]

thank you for your help,i will try it.