Find an array element's index

I have a first array that has about 5000 values. I have a second array that is (first array - (0.3)*(first array(1))); For every element in the first array, I must find the value and index of the closest element in the second array. Any help is highly appreciated.

[Jan]

What have you tried so far? Is this a homework? Did you search in the forum already?

Answer 1

[Image Analyst]

Did you try the obvious min() function????

[closestValue, indexOfClosestValue] = min(abs(array1-array2));

Make sure array1 and array2 are not uint8 or uint16 though. Cast to double first, if you're using one of them.

Answer 2

[A VP]

What I have currently is this :

temp = zeros(1,length(x)); 
min_val = zeros(1,length(x)); 
index = zeros(1,length(x)); 
y = x- (0.3)*(x(1)); 
for i=1:length(x) 
    for j = 1 : length(x) 
        temp(j) = abs(y(i)-x(j)); 
        if j == length(x) 
            [min_val(i), index(i)] = min(temp); 
        end 
    end 
end

x is the initial array, y is the final array. y is an array formed by subtracting 30% of the first value of x from each element of x. I should be able to find the closest match of y in x and find its index in x. This logic works well for a smaller array, but the nested for loop takes forever for an array with large number of values. I have arrays with 6-digit numbers. Is there a quicker way of doing this?

[Image Analyst]

But your temp is always a constant. Since y = x-constant, then y-x is x-(x-constant) which equals the constant. So it's the same everywhere. All elements have the same value, which is 0.3*x(1).