How to fixe the For loop

Question

0 个投票

Hello. Could anyone tell me how to fix the for-loop code?

>>

b = {'Hello world'; 'Good morning';'Good afternoon';'6 years';'10+ years';'<1 year'}

z=array2table(b,'VariableNames', {'var1'})

for i=1:length(z)

if z(i,1)='Hello world'; z(i,1)=1;

else z(i,1)=0;

end

Output:

b =

6×1 cell array

{'Hello world' }

{'Good morning' }

{'Good afternoon'}

{'6 years' }

{'10+ years' }

{'<1 year' }

z =

6×1 table

var1

__________________

{'Hello world' }

{'Good morning' }

{'Good afternoon'}

{'6 years' }

{'10+ years' }

{'<1 year' }

if z(i,1)='Hello world'; z(i,1)=1;

↑

Incorrect use of '=' operator. Assign a value to a variable using '=' and compare values for equality using '=='.

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Answer 1

Star Strider 2021-4-23

在 MATLAB Online 中打开

0 个投票

Do exactly this:

compare values for equality using '=='

However the actual solution is likely the strcmp (or related strcmpi) function.

Try this:

b = {'Hello world'; 'Good morning';'Good afternoon';'6 years';'10+ years';'<1 year'}
z=array2table(b,'VariableNames', {'var1'})
     for i=1:height(z)
         
        if strcmp(z{i,1}, 'Hello world'); z{i,1}={1};  
            
        else z{i,1} = {0};
            
        end 
     end

Indexing correctly (here using curly braces {}) is important.

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Oleksandr Puchak 2021-4-23

Star Strider, Thank you for pointing strcmp to me - it is very useful. Code that you suggest works after a slight adjustment. Thank you.

b = {'Hello world'; 'Good morning';'Good afternoon';'6 years';'10+ years';'<1 year'}

z=array2table(b,'VariableNames', {'var1'})

for i=1:height(z)

if strcmp(z{i,1}, 'Hello world')==1; z{i,1}={1};

else z{i,1} = {0};

end

Star Strider 2021-4-23

My pleasure!

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Answer 2

DGM 2021-4-23

编辑：DGM 2021-4-23

在 MATLAB Online 中打开

0 个投票

You need to use == for equality tests, not =. That said, don't try testing character arrays for equality that way either. Unless they have the same number of characters, you'll have problems. Use strcmp(), strcmpi(), or ismember().

b = {'Hello world'; 'Good morning';'Good afternoon';'6 years';'10+ years';'<1 year';'0'}
z=array2table(b,'VariableNames', {'var1'})
for i=1:height(z) % use height/width/size/numel, not length
    if strcmp(z{i,'var1'},'Hello world'); % use curly braces for indexing here.  you can either use column number or name
        z{i,'var1'}={'1'}; % i'm assuming that elements of a table column should share the same datatype
    elseif strcmp(z{i,'var1'},'0'); % if there's a condition, use elseif instead of else
        z{i,'var1'}={'something else'};	
    else
        % do something else
    end
end
z % see what changed

gives

z = 
          var1      
    ________________
    'Hello world'   
    'Good morning'  
    'Good afternoon'
    '6 years'       
    '10+ years'     
    '<1 year'       
    '0'             
z = 
          var1      
    ________________
    '1'             
    'Good morning'  
    'Good afternoon'
    '6 years'       
    '10+ years'     
    '<1 year'       
    'something else'