如何收集元素之間具有相同長度的數組X的索引

Question

我正在試圖創建一個數組Z，它的索引是數組X中最常出現的兩個元素之間的差異。因此，如果最頻繁發生在X的兩個元件之間的差爲3，那麼我會得到所有在X具有該差成陣列Z.

x = [ 0.2 0.4 0.6 0.4 0.1 0.2 0.2 0.3 0.4 0.3 0.6]; 
ct = 0; 
difference_x = diff(x); 
unique_x = unique(difference_x); 
for i = 1:length(unique_x) 
    for j = 1:length(x) 
      space_between_elements = abs(x(i)-x(i+1)); 
      if space_between_elements == difference_x 
       ct = ct + 1; 
       space_set(i,ct) = j; 
      end 
    end 
end 

我不得到X的含有來自該代碼最頻繁的差的索引的索引。

Answer 1

看樣子你想找到多少獨特的差異性有，用「差異化」在absoulte價值感解釋;並且還發現每個差異發生多少次。

你能做到這一點，如下所示：

x = [ 0.2 0.4 0.6 0.4 0.1 0.2 0.2 0.3 0.4 0.3 0.6]; %// data 
difference_x = abs(diff(x)); 
unique_x = unique(difference_x); %// all differences 
counts = histc(difference_x, unique_x); %// count for each difference 

然而，對於唯一（或等於）比較實數爲problematic，因爲有限的精度。你還是應用公差申報兩個值是「平等」：

x = [ 0.2 0.4 0.6 0.4 0.1 0.2 0.2 0.3 0.4 0.3 0.6]; %// data 
tol = 1e-6; %// tolerance 
difference_x = abs(diff(x)); 
difference_x = round(difference_x/tol)*tol; %// apply tolerance 
unique_x = unique(difference_x); %// all differences 
counts = histc(difference_x, unique_x); %// count for each difference 

你的榜樣x，第二種方法給出

>> unique_x 
unique_x = 
     0 0.1000 0.2000 0.3000 
>> counts 
counts = 
    1  4  3  2