How do I assign the output from a Matlab function to a variable in a single line?

问题

Is there a way in matlab to assign the output from a function in matlab to a vector within a single line?

For example, this function should assign a perimeter and an area value

function [p,a] = square_geom(side)
p = perimeter_square(side)
a = side.^2
[p,a]

however when I try to store the data like this

v = square_geom(3)

It doesn't work. However it is possible to do it like this

[p,a] = square_geom(3)
v=[p,a]

But that just doesn't look as good as keeping it to a single line. Any ideas?

回答1:

You can change the definition of your function by using varargout as output variable:

Edit Updated the definition of the function to include the check on the number of output

function varargout = square_geom(side)

p = 3;% %perimeter_square(side)
a = side.^2;
v=[p,a];

switch(nargout)
   case 0 disp('No output specified, array [p,a] returned')
          varargout{1}=v;
   case 1 varargout{1}=v;
   case 2 varargout{1}=p;
          varargout{2}=a;
   case 3 varargout{1}=v;
          varargout{2}=p;
          varargout{3}=a;
   otherwise disp(['Error: too many (' num2str(nargout) ') output specified'])
             disp('array [p,a,NaN, NaN ...] returned (NaN for each extra output)')
             varargout{1}=v;
             varargout{2}=p;
             varargout{3}=a;
             for i=4:nargout
                varargout{i}=NaN
             end
end

This allows you either calling your function in several ways

square_geom(3)
v=square_geom(3)
[a,b]=square_geom(3)
[a,b,d]=square_geom(3)
[a,b,d,e,f,g]=square_geom(3)

In the first case you get the array v as the automatic variable ans

square_geom(3)

No output specified, array [p,a] returned
ans =

   3   9

In the second case, you get the array v

v=square_geom(3)

v =

   3   9

In the third case, you get the two variables

[a,b]=square_geom(3)

a =  3
b =  9

In the fourth case, you get the array v and the two sigle variables a and b

[v,b,d]=square_geom(3)

v =

   3   9

b =  3
d =  9

In the latter case (too many output specified), you get the array v, the two single variables a and b and the exceeding variables (e, f and g) set to NaN

[v,b,d,e,f,g]=square_geom(3)

Error: too many (6) output specified
array [p,a,NaN, NaN ...] returned (NaN for each extra output)
v =

   3   9

b =  3
d =  9
e = NaN
f = NaN
g = NaN

Notice, to thest the code I've modified the function byh replacing the call toperimeter_square with 3

回答2:

The value outputted by the function are two different variables, not an array. So the output should be stored as two cells.

[v(1),v(2)]=fn(val)

Here, the value is stored in two different cell v(1) and v(2) of the same array 'v'.

回答3:

The simplest solution that comes into my mind is:

c = test();

function result = test()
    a = ...; % complex computation
    b = ...; % complex computation

    result = [a b];
end

The C variable will then be a column vector containing two values. But this solution is only suitable if your function output doesn't need to be flexible.