Operands to the || and && operators must be convertible to logical scalar values.

Question

Skydriver 2019-6-6

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https://ww2.mathworks.cn/matlabcentral/answers/465924-operands-to-the-and-operators-must-be-convertible-to-logical-scalar-values

评论： Skydriver 2019-6-9

I have a problem with my coding about Operands to the || and && operators must be convertible to logical scalar values.. Here in detail:

for i=1:length(FS);
  depth_all7=[]
  if FS < 1 && Depth<20;  
    LPi= (1-FS(i))*(J - K*Depth(i));
  elseif FS>= 1 && Depth > 20
    LPi= 0;
  elseif FS <=1 && Depth>=20
    LPi = 0;    
  elseif FS >=1 && Depth<=20
    LPi= 0;  
    depth_all7=[depth_all7;LPi]
  end     
  fprintf(fid_X,'%2.4f  %2.4f  %2.4f %2.4f %2.6f %10s\n', Depth(i),CSR(i), CRR(i), FS(i), LPi(i), teks_i);
end

Is there any one can help me?

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Answer 1

dpb 2019-6-6

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https://ww2.mathworks.cn/matlabcentral/answers/465924-operands-to-the-and-operators-must-be-convertible-to-logical-scalar-values#answer_378191

编辑：dpb 2019-6-7

在 MATLAB Online 中打开

Presuming FS and Depth are vectors, then you need to subscript them as, for example

if FS(i) < 1 && Depth(i)<20

in all expressions...otherwise FS<1 or Depth>=20 return logical vectors of size(FS) or size(Depth)

You can do the assignments using logical addressing without the loop...note as you've written the loop that the depth_all7 array will be equivalent to

depth_all7=zeros(sum(FS>=1 & Depth<=20,1));

so numel() will be the number of cases that satisfy the condition, not the same size as Fs. If that is the intent, that's fine.

The first conditional case is peculiar -- if LPi is a single value not a predefined array, then it is overwritten each pass through the loop and otherwise never used. One would guess that isn't the intent.