MATLAB Answers


Expected a scalar error

Asked by Arkanra Kadhum on 25 Feb 2019
Latest activity Commented on by Arkanra Kadhum on 25 Feb 2019
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) ;
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')
if n==1 && K1==1
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


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Hi Roberson
Thank you for your replay answer. These variables are column vector as 3, 7,1
My problem is to read the inputs column then sorted accident and change the output ascending order corroding to their indices. So to send 1 to Y1 , 3 to Y2 and 7 to Y3.
The problem is in using K1, K2 and K3 with if statement, so how can I change them from vector to scalar.
Please replace last line by
Best regards
Walter Roberson
on 25 Feb 2019
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.
thank Roberson it is work

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1 Answer

Walter Roberson
Answer by Walter Roberson
on 25 Feb 2019
 Accepted Answer

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.


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