problem with if condition

hi, i have this problem with matlab. This is my m-file, but it doesnt work.

clear all
t=0:0.1:1;
k=length(t);
a=0;
for i=1:k
    if a==0.8       
        disp('hi')
    end
    a=a+0.1
end

If i use this one
t=0:1:10;
k=length(t);
a=0;
for i=1:k
    if a==8       
        disp('hi')
    end
    a=a+1
end

this one works well. The difference between first and second case is only that some variables are increased 10times. Please help. thank you

Answer 1

[Aldin]

Solution:

Here, try this algorithm:

    clear all
    t=0:0.1:1;
    k=length(t);
    a=0;
    for i=1:k
        b = num2str(a);
        if strcmp(b,'0.8');       
            disp('hi')
        end
        a=a+0.1;
    end

[milan pepa]

thank you

Dont you know the reason why it works wrong in second case?

[Aldin]

I don't know. Maybe cause 0.8 is not equal to 0.8000 by using for loop.

Are you from Yugoslavia?:) See Walter Roberson link:

http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

[Aldin]

Accept Answer if i was helpful.

[Walter Roberson]

Using the string solution is not recommended. Instead use a tolerance on the comparison.

[milan pepa]

thank you Walter, it works great

Answer 2

[G A]

http://www.mathworks.co.uk/support/solutions/en/data/1-16FOQ/?solution=1-16FOQ

and this:

http://www.mathworks.co.uk/support/tech-notes/1100/1108.html

[Walter Roberson]

http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

[milan pepa]

thank you