The Variable appears to change size on every loop iteration

    [num_class,num_instance]=size(Outputs);
     temp_Outputs=[];
    temp_test_target=[];

    for i=1:num_instance
        temp=test_target(:,i);
        if((sum(temp)~=num_class)&&(sum(temp)~=-num_class))
            *temp_Outputs=[temp_Outputs,Outputs(:,i)]; 
            temp_test_target=[temp_test_target,temp];*
        end
    end

Error: The Variable "temp_Outputs" appears to change size on every loop iteration

Question : I have No clue how to Preallocate it ?? Please help !!

Answer 1

[per isakson]

This is not an error, it's a warning. It is inefficient to change size of a variable in a loop.

However, the if-statement makes it difficult to know the final size in advance, which is "needed" to preallocate.

IMO: don't care about the warning if the execution time is ok. It is possible to suppress it.

See:

• Techniques for Improving Performance
• Understanding Array Preallocation
• Preallocation performance

[pooja]

oh thank you for this information

and sorry , i wrote there "error" by mistake

[per isakson]

Check the links I provided. They are in the order from basic to advanced. There is no single sentence answer.

[Mahmoud Emad]

What if I had an execution time problem with a code very similar to this, my vector also is created by conactenation in a for loop, is there an efficient alternative ?