Expected a scalar error

Question

Arkanra Kadhum 2019-2-25

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/446791-expected-a-scalar-error

评论： Arkanra Kadhum 2019-2-25

I used fun block in simulink with the following program

function [Y1, Y2,Y3]   = selectionSort( Vc1,   Vc2,   Vc3)
A=[ Vc1,   Vc2,   Vc3];
B = sort(A) ; 
B1=B(1);B2=B(2);B3=B(3);
 Y1=0; Y2=0; Y3=0; 
 
K1=find(A==B(1),1, 'first')
K2=find(A==B(2),1, 'first')
K3=find(A==B(3),1, 'first')
 
n=1 
if n==1 && K1==1
     Y1=1;Y2=0;Y3=0;Y4=0;Y5=0;Y6=0;Y7=0;Y8=0;Y9=0;Y10=0;
end

I get this error

Expected a scalar. Non-scalars are not supported in IF or WHILE statements, or with logical operators. Instead, use ALL to convert matrix logicals to their scalar equivalents. Function 'MATLAB Function' (#207.737.742), line 19, column 12: "K1==1"

Please I need your help to solve this problem

4 个评论
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Walter Roberson 2019-2-25

Well, change the code to use all(K1==1) like it suggests. Sometimes you have to take some extra steps because Simulink's automatic checking is not as intelligent as humans are.

Arkanra Kadhum 2019-2-25

thank Roberson it is work

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Answer 1

Walter Roberson 2019-2-25

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/446791-expected-a-scalar-error#answer_362555

Your code is too complex for MATLAB to be able to prove that all of the B values are certain to compare equal to part of A, so MATLAB has to assume that the find() can return empty.

By the way, some of the values can be empty, if there are nan in the inputs.

If the exercise is to implement selection sort, then you are unlikely to pass with that sort() call in your code. Might as well just call sort() with two outputs and use the returned indices.