strings and numbers for a numeric array name

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yasmine 2011-12-15

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I am using 6 numeric arrays in my project, their names are: block1, block2 , block3 , block4, block5 , block6

i execute the same function for all of them, i need to make this in a for loop, but i failed to index the elements of the arrays, i tried this:

   for i=1:6
        h = ['block' int2str(i)];
        eval(h)
    end
                for row=1:BRows
                 for col=1:BCols
                if (h(row,col) >= 316 &&  h(row,col) <= 20)
                    h(row,col) = 0;
            elseif (h(row,col) >= 21 &&  h(row,col) <= 40)
                    h(row,col) = 1;
                end
                end

Would you help me please

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yasmine 2011-12-16

i tried it but this error occurred:

??? Error: File: fg6.m Line: 86 Column: 40

The expression to the left of the equals sign is not a valid target for an assignment.

any other suggestions?

Jan 2011-12-16

The problem is, that your "h" is *not* the contents of block1, but the string 'block1'. Avoid EVAL.

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the cyclist 2011-12-15

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Rather than doing it like that, I strong suggest you used cell arrays, as described in Doug's answer here: http://www.mathworks.com/matlabcentral/answers/143-how-do-i-make-a-series-of-variables-a1-a2-a3-a10

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yasmine 2011-12-16

actually i have a problem with cell arrays in my project, i can't use them

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Jan 2011-12-16

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Please explain why you cannot use cell arrays. "eval([block, int2str(i)])" is such an ugly approach, prone to errors and it has remarkable drawbacks for the processing speed in Matlab. I cannot imaging why "h=block{i}" should be worse. Embedding an index in the name of a variable is not smart. Better use an index as index.

Btw. you do not want to do "eval(h)", but:

eval(['h = block', int2str(i)]);

As you see: The EVAL approach is prone to errors!