MATLAB: Error:Conversion to cell from double is not possible.

cell arraydoubleif statementmatrixmatrix array

Dear Programmers

I have a below written code in which I want to run a logical algorithm based on parameters HP and SS with if-else. YM is another parameter which will store the results of the logical statements. HP and SS are 2 cell-array columns which are derived from stress array. YM is another cell-array columns derived a matrix E. "for" loop is executed from row 1 to last row of the stress array so that the values of HP and SS can be evaluated in each row to give a desired value of YM in the YM cell-array following the logical statements.

While executing the code I am receiving the error message: Conversion to cell from double is not possible.

Please help !

N.B: I have attached the txt file for reference.

fID = fopen('no_header.txt','r');
stress=textscan(fID,'%n %n %n','headerlines',7,'Delimiter','');
fclose(fID);
 E = zeros(size(stress{1,1}));
 YM= num2cell(E);
 HP= num2cell(stress{1,2});
 SS= num2cell(stress{1,3});
for i= 1:size(stress{1,1},1)
if HP{i}==0 & SS{i}==0
        YM(i,1) =1;
elseif HP{i} > 0.15 & SS{i}==0
       YM(i,1) = 2;
elseif HP{i} > -0.15 & SS{i} > 5
       YM(i,1) = 2;
elseif HP{i} > -0.15 & SS{i} < -5
       YM(i,1) = 2;
 elseif HP{i} < -0.15
       if SS{i} < -15 | SS{i} > 15 
            YM(i,1) = 10;
       else 
           YM(i,1) = 1000; 
end
elseif HP{i} > -0.15 & HP{i} < 0.15 & SS{i} > -5 & SS{i} < 5
           YM(i,1) = 6000;
else
        warning('CURRENT VALUES OF HP AND SS NOT COVERED BY THIS SIMULATION')
        
    end
  end

Best Answer

Since YM is cell, you need use curly braces { } for indexing to access the contents of cells. YM(i,1) in lines 10, 12, .. 24 has to be replaced to YM{i,1}

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MATLAB: Error:Conversion to cell from logical is not possible.

It's difficult to follow a conversation when some comments have been deleted... I cannot see any table in any of the code that has been posted.

Anyway, one thing for sure,

if {any_expression}

has never been valid syntax in matlab and will indeed result in the error mentioned in the title of the question. The {} are not valid here. While in maths, you can use {} as brackets similar to (), in matlab it means something completely different. The correct syntax is

if any_expression

Making up your own syntax is not going to be very succesful. You need to read the documentation and use the exact same syntax that is stated. Another made up syntax is

-0.15 < SS < 0.15

While this will not throw an error, it will certainly not produce the result desired. The above will evaluate first -0.15 < SS which will produce a true (1) result or false (0) result. It will then compare that 0 or 1 with 0.15. The end result is that the expression produces a true result for any SS <= -0.15 and false otherwise. Not what was intended at all!

The correct expression is:

-0.15 < SS && SS < 0.15

Also note that

if (HP > 0.15)||((HP > -0.15 )&& (SS > 0.05))||((HP > -0.15 )&& (SS < -0.05))

reduces to simply:

if HP > 0.15

Finally, note that the preallocation of E and V should be done outside the loop and since E and V are meant to contain numbers they shouldn't be allocated as logical but as double. So, code with all the mistakes removed:

E = zeros(size(m, 1), 1);  %preallocation done the right way
V = zeros(size(m, 1), 1);
for i= 1:size(m, 1)  %don't hardcode size of arrays (with you n = 1000). Ask matlab for it, so that if the array size changes you don't have to do a thing
    HP = m(i,1);
    SS = m(i,2);
    if HP==0 && SS==0
        E(i,1) = 1;
        V(i,1) = 0.167; 
    elseif HP > 0.15
        E(i,1) = 2;
        V(i,1) = 0.167;         
    elseif HP < -0.15  %splitting the expression for clarity
        if SS < -0.15 || SS > -0.15 
            E(i,1) = 10;
            V(i,1) = 0.167; 
        else
            E(i,1) = 1000;
            V(i,1) = 0.3; 
        end
    elseif HP > -0.15 && HP < 0.15 && SS > -5 && SS < 5
        E(i,1) = 6000;
        V(i,1) = 0.3;
    else
        warning('current values of HP and SS not covered by the tests')
    end
end

Note that as with your original code, the cases where

HP == -0.15 || HP == 0.15
HP is not between -0.15 and 0.15 and SS is greater than 5 or smaller than -5

are not covered by any of the tests, So E an S will stay 0. At least I'm warning you in these cases.

Unlike your original code, the case where HP is <-0.15 and SS is either -0.15 or 0.15 is covered by my tests. It's considered the same as SS being between -0.15 and 0.15.

MATLAB: How to select element of an array between two values

A(A > -0.15 & A < 0.15)

A(abs(A) < 0.15)

Best Answer

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MATLAB: Error:Conversion to cell from logical is not possible.

MATLAB: How to select element of an array between two values

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