problem in return of function

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huda nawaf
huda nawaf 2012-9-1
Hi, I have the following code
function [c,d]=test2(a,b)
if a>1
c=a*b';
d=a+b;
else
c=a*b'
end
In case of a be >1 I got this error message: Error in ==> test2 at 2 if a>1
??? Output argument "d" (and maybe others) not assigned during call to
"D:\MATLAB\R2011a\bin\test2.m>test2".
thanks
[EDITED, Jan, code formatted]
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Image Analyst
Image Analyst 2012-9-2
No. You don't need to "make spaces between each two lines" (each pair of lines). You just make sure there is a blank line before the first line of your code. Then you highlight ALL your code, which may include blank lines or not - it doesn't matter, just highlight everything. Then click {}Code and it will format everything properly, even going across chunks of your code where you have a blank line.
Oleg Komarov
Oleg Komarov 2012-9-2
@huda: then you weren't looking carefully. In the .gif I format the code, and then I improve it a bit. You can forget about the second part, just watch what happens when I press {}code in the preview.

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回答（3 个）

Star Strider
Star Strider 2012-9-1
编辑：Star Strider 2012-9-1
If it is not always necessary for you to return a value for ‘d’, you might consider using the nargout function.
For example:
function [c,d]=test2(a,b)
if (nargout > 1) && (a > 1)
c=a*b';
d=a+b;
elseif (nargout == 1) && (a <= 1)
c=a*b'
end
So if your calling function calls test2 with (a <= 1), only needs ‘c’ and does not need ‘d’, this version of your function would only return a value for ‘c’. You would not generate the error. You can experiment with different options.
Image Analyst
Image Analyst 2012-9-1
编辑：Image Analyst 2012-9-1
So when you pass in a value of a less than 1, what value does d have? Think about it. It could be written more robustly like this perhaps:
function [c ,d] = test2(a, b)
% Initialize outputs to null.
c = [];
d = [];
try
% b is apparently an array because he's using the transpose operator '.
% a must be a scalar since he's comparing it to 1.
% c is the same for both parts of the if so we can pull it out of the if.
% We have no idea what d was supposed to be in case a < 1
% So we'll just assign it to a string.
c = a * b';
if a > 1
d = a + b;
else
% Assign d to a string or whatever you want.
d = 'a is less than 1';
end
catch ME
errorMessage = sprintf('Error in function test2.\n.\n\nError Message:\n%s', ME.message);
uiwait(warndlg(errorMessage));
end
Yash
Yash 2012-9-1
编辑：Yash 2012-9-1
for any values less then one it will give the following output
[c,d]=test2(-2,4)
c =
-8
Error in ==> test2 at 2 if a>1
??? Output argument "d" (and maybe others) not assigned during call to "D:\MakeYourassignment.com\test2.m>test2".
however change the code to this if you dont want any such error to exist..
function [c,d]=test2(a,b)
if a>1
c=a*b';
d=a+b;
else
c=a*b';
d=0;
end
now the output will be
[c,d]=test2(-2,4)
c =
-8
d =
0

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