MATLAB: Are the inequality expressions not evaluated correctly

logical expressionmisplaced parenthesis

My code is: grid is just a 5×6 matrix, so is visited.

neighbor=[3 4]
if((neighbor(1)>0) && (neighbor(1)<size(grid,1)+1) && (neighbor(2)>0) && (neighbor(2)<size(grid,2)+1) && (visited(neighbor(1),neighbor(2)==-1)))

Matlab gives the following error: Operands to the and && operators must be convertible to logical scalar values.

What's going wrong? I tried to debug step by step but could not figure out the mistake.

Best Answer

Perhaps you meant:

if((neighbor(1)>0) && (neighbor(1)<size(grid,1)+1) && (neighbor(2)>0) && (neighbor(2)<size(grid,2)+1) && (visited(neighbor(1),neighbor(2))==-1))

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MATLAB: Function Error / If and elseif statement help

As a replacement for what you have done here, I would suggest using ismember to find the triples that form valid codes. You can even use it to keep track of every marked position so you can see if you forgot to implement any triples.

amino_acid_chain = cellstr(reshape(neucleotide_string,3,[])');
L=false(size(amino_acid_chain));%keep track of replaced codes
library={{'E','GAA','GAG'};...
    {'W','UGG'}};%etc
for n=1:numel(library)
    triplet=library{n}(2:end);%select the triplet(s) from the library (e.g. {'GAA','GAG'})
    letter=library{n}(1);%select the corresponding amino acid letter (e.g. 'E')
    L_current_code=ismember(amino_acid_chain,triplet);%find all positions where the amino acid occurs
    amino_acid_chain(L_current_code)=letter;%replace by the letter code
    L=L | L_current_code;%mark as replaced
end
if any(~L)%shouldn't happen
    error('some code was not implemented correctly')
end

MATLAB: How to make function which gets as input arguments matrix of chars work

Kevin's Answer Is Correct Of Course,

But If that Was The Problem You Were Facing You Would Have Had A Different Error About Indexing Mismatch or SWITCH expression must be a scalar or a character vector.

I suspect you called the translation function with a character vector input, something like:

a = translation('GCUGAC')

the problem is that when you test the value at index m of that codons vector you get a single character 'G', 'C', 'U' or 'A' which is never equal to any of the sequences in your switch case.

what you need to do is send the codon sequence as a cell array of character vectors:

a = translation({'GCU' 'GAC'})

then you need to index that inside the loop with curly bracers like kevin said:

switch (codons{m})

and the output should also be a cell array proobably (like kevin suggested)

moreover, it's always a good idea to add a default value for output arguments, add

aminoacids = {};

just before the loop.

Best Answer

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MATLAB: Function Error / If and elseif statement help

MATLAB: How to make function which gets as input arguments matrix of chars work

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